WO2017164616A1

WO2017164616A1 - Methods for preparing 3'-amino-2',3'-dideoxyguanosine by using nucleoside phosphorylases derived from bacillus and adenosine deaminase derived from lactococcus

Info

Publication number: WO2017164616A1
Application number: PCT/KR2017/003016
Authority: WO
Inventors: Kap Soo Noh; Kang Hyun Choi; Byung Kyun Kim
Original assignee: St Pharm Co., Ltd.
Priority date: 2016-03-21
Filing date: 2017-03-21
Publication date: 2017-09-28
Also published as: KR20170109376A; KR101818564B1

Abstract

The present invention relates to a method for preparing 3'-amino-2',3'-dideoxyguanosine using Bacillus stearothermophilus-derived nucleoside phosphorylases and Lactococcus lactis-derived adenosine deaminase. According to the method for preparing 3'-amino-2',3'-dideoxyguanosine of the present invention, 3'-amino-2,3'-dideoxyguanosine can be mass-produced efficiently and economically through high rate of enzymatic conversion and high purity of purifications.

Description

METHODS FOR PREPARING 3'-AMINO-2',3'-DIDEOXYGUANOSINE BY USING NUCLEOSIDE PHOSPHORYLASES DERIVED FROM BACILLUS AND ADENOSINE DEAMINASE DERIVED FROM LACTOCOCCUS

The present invention relates to a method for preparing 3'-amino-2',3'-dideoxyguanosine using Bacillus-derived nucleoside phosphorylases and Lactococcus-derived adenosine deaminase.

Extensive studies on the use of oligonucleotide and oligonucleotide analogue drugs based on binding to specific nucleic acid sequences or proteins have been conducted. Particularly, oligonucleotide analogue drugs have been studied so that their resistance to nuclease and their binding force and specificity for other substances can be improved.

Oligonucleotide analogue drugs have been designed so that their resistance to nuclease and their binding force and specificity for other substances can be improved. Among them, N3' O5' phosphoramidates are known to be stable even in double helices and triple helices and to have higher resistance to nuclease compared to common DNA or RNA (J. K. Chen et al., Nucleic Acids Res., 23, 2661-2668 (1994); C. Escude et al., Proc. Natl. Acad. Sci. USA, 93, 4365-4369 (1996); S. M. Gryaznov et al., Nucleic Acids Res., 24, 1508-0514 (1996); C. Giovannangeli et al., Proc. Natl. Acad. Sci. USA, 94, 79-84 (1997)). These phosphoramidates may be used as DNA hybridization probes and PCR primers having a high selectivity for RNA sequences having a low copy number. However, the biggest problem in the use of such compounds is that it is difficult to prepare 3'-amino-nucleoside.

3'-azido-3'-deoxythymidine(AZT) has been used as a precursor for the research development of chemical and enzymatic method for preparing of 3'-amino-2',3'-dideoxyguanosine(ADG). 3'-azido-3'-deoxythymidine (AZT) is an important pharmaceutical raw material found to have anti-human immunodeficiency virus activity, and is prepared using thymidine (TMD) as a raw material (N. Miller et al., J. Org. Chem., 29, 1772-1776 (1964); Horwitz et al., J. Org. Chem., 29, 2076-2078 (1964)). It is industrially produced in large amounts and is easily available.

As a chemical preparation method for 3'-amino-2',3'-dideoxyguanosine, a method is known in which 3'-azido-3'-deoxy-5'-O-acetylthymidine is prepared using 3'-azido-3'-deoxythymidine as a raw material, and then substituted with N²-palmitoylguanine (M. Imazawa et al., J.O.C., 43(15): 3044 (1978)). However, in this method, isolation and purification are difficult due to mixed production of α-anomer, and the preparation yield is very low (28%), indicating that this method has a very low efficiency.

As a method using chemistry and enzymes, a method is known in which 3'-azido-3'-deoxythymidine is chemically reduced into 3'-amino-2',3'-deoxythymidine (ATMD) which is then treated with thymidine nucleoside phosphorylase and purine nucleoside phosphorylase enzymes from Escherichia coli BMT-38 cells, thereby preparing 3'-amino-2',3'-dideoxyguanosine (G. V. Zaitseva et al., Nucleosides & Nucleotides, 13(1-3): 819 (1994)). However, the literature of G. V. Zaitseva reported that 3'-amino-2',3'-dideoxyguanosine was produced by adding 250 mg (1.04 mmol) of 3'-amino-3'-deoxythymidine, 320 mg (1.13 mmol) of guanosine and 2 g of dry E. coli BMT-38 to 30 mL of 5 mM phosphate buffer (pH 6.75) reaction solution, and allowing the mixture to react 50°C for 28 hours, followed by purification using ion exchange resin. The yield (20.5%) of this method was not sufficient due to low efficiency.

Furthermore, according to US Patent Publication No. 2007/0065922, Escherichia coli 1K/1T showing high activities of a thymidine phosphorylase (TPase) and purine nucleoside phosphorylase (PNPase) was selected and used in a reaction. Specifically, 100 mM (2.42 g) of 3'-amino-3'-deoxythymidine, 50 mM (0.75 g) of 2,6-diaminopurine (DAP) and either 3 g of Escherichia coli 1K/1T wet cells pretreated with glutaraldehyde or purified TPase (1250 IU) and PNPase (950 IU), were added to 100 ml of 20 mM phosphate buffer (pH6.0) reaction solution, and reacted at 50°C for 16-24 hours, followed by purification using ion exchange resin, thereby preparing 1.04-1.15 g (a molar yield of 39-43% based on 3'-amino-3'-deoxythymidine added) of 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside (ADDAP). Then, 167 mM (2.65 g) of the prepared 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside and 15-20 μl of adenosine deaminase (5 mg/ml, Boehringer Mannheim) were added to 60 ml of purified water, and reacted at 50° or below for 24-48 hours, followed by purification, thereby preparing 2.46 g of 3'-amino-2',3'-dideoxyguanosine. Namely, the above US Patent Publication describes that 3'-amino-2',3'-dideoxyguanosine was prepared in a molar yield of about 38% from 3'-amino-3'-deoxythymidine.

However, the above-described transglycosylation methods based on bioconversion has the following problems, and thus the commercial use thereof is very limited.

First, the industrial application of the methods is not efficient, because the molar yield is at most about 38% based on 3'-amino-3'-deoxythymidine that is a main raw material.

Second, the amount of microbial cells used to convert 10 mmol (2.42 g) of 3'-amino-3'-deoxythymidine reaches about 3 g, and when such a large amount of microbial cells are used, industrialization is impossible due to the raw material cost for preparing the microbial cells, the process time required to remove the microbial cells after completion of bioconversion, and a decrease in the yield.

Third, in the above-described prior art documents, the reaction was performed using the main raw material at a very low concentration of 10-100 mM. However, at such a low concentration, industrial application is impossible. For this reason, in order to increase equipment efficiency and production efficiency, it is required to establish high-concentration reaction conditions. However, the prior art documents do not disclose such reaction conditions.

Fourth, the enzymatic conversion method requires pretreatment of microbial cells with glutaraldehyde in order to prevent the microbial cells from being disrupted at a relatively high temperature of 50°C (P. H. Ninh et al., Appl. Environ. Microbiol.,79(6), 1996-2001 (2013)).

Fifth, in the above-described prior art documents, the molar ratio between reaction substrates shows a difference of 2-3 times in order to increase the transglycosylation yield, and thus a large amount of unreacted materials remain after completion of enzymatic conversion to impose a burden on subsequent purification and to cause of rise the material cost in industrial terms.

Sixth, the purification method using ion exchange resin also has problems in that a separate resin tower is required in process design and in that the addition of adsorption and desorption processes and a process for concentration of product fractions increases the process time and the production cost.

Under this background, there is a need to select suitable enzymes, which can reduce the difference in molar ratio between substrates at high concentrations and increase the transglycosylation yield, and to perform research and development on the optimization of transglycosylation reactions. Furthermore, there is a need to develop a method capable of economically and efficiently purifying pure 3'-amino-2',3'-dideoxyguanosine from a reaction solution after completion of bioconversion as described above.

The present invention provides a method for preparing 3'-amino-2',3'-dideoxyguanosine, comprising the steps of: (a) preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase; and (b) preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase.

The present invention also provides a method for preparing 3'-amino-2',3'-dideoxyguanosine, further comprising, after step (b) of preparing 3'-amino-2',3'-dideoxyguanosine, step (c) of removing the sources of purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes, and reaction byproducts by adding an alcohol and a strong base to the reactant of step (b).

The present inventors have made extensive efforts to develop a method for industrial production of a large amount of 3'-amino-2',3'-dideoxyguanosine, and as a result, have found that when 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside is prepared in high yield using Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase and is treated with Lactococcus lactis-derived adenosine deaminase, a high purity of 3'-amino-2',3'-dideoxyguanosine can be prepared in a higher yield compared to when a conventional known method is used, thereby completing the present invention.

The present invention provides a method for preparing 3'-amino-2',3'-dideoxyguanosine, comprising the steps of: (a) preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase; and (b) preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase.

In the present invention, 3'-amino-2',3'-dideoxyguanosine is a compound having a structure of the following formula 1:

[Formula 1]

In the present invention, 3'-amino-3'-deoxythymidine is a compound having a structure of the following formula 2:

[Formula 2]

In the present invention, 2,6-diaminopurine is a compound having a structure of the following formula 3:

[Formula 3]

In the present invention, 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside is a compound having a structure of the following formula 4:

[Formula 4]

In the present invention, thymine is a compound having a structure of the following formula 5:

[Formula 5]

In the present invention, nucleoside phosphorylase (NP) refers to an enzyme that causes phosphorolysis of a N-glycosidic linkage in the presence of phosphate, and catalyzes a reaction represented by the following equation:

Ribonucleoside + phosphate nucleic acid base + ribose-1-phosphate

The method for preparing 3'-amino-2',3'-dideoxyguanosine according to the present invention shows a high rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by use of Bacillus stearothermophilus-derived nucleoside phosphorylases, and thus provides an intermediate capable of efficiently producing a large amount of 3'-amino-2',3'-dideoxyguanosine. Particularly, the method using the enzymes according to the present invention shows a significantly high ability to produce 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside, compared to a preparation method using the purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase derived from other strains, or a preparation method using other nucleoside phosphorylases.

The bioconversion process according to the present invention, which reacts 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase, is explained by the following two-step transglycosylation process:

1) Pyrimidine nucleoside phosphorylase reaction

3'-amino-3'-deoxythymidine + phosphate thymine + 3-amino-2,3-dideoxyribose-1-phosphate

2) Purine nucleoside phosphorylase reaction

2,6-diaminopurine + 3-amino-2,3-dideoxyribose-1-phopsphate 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside + phosphate

As shown in the above reactions, pyrimidine nucleoside phosphorylase substitutes 3'-amino-3'-deoxythymidine with 3-amino-2,3-dideoxyribose-1-phosphosphate, and 3-amino-2,3-dideoxyribose-1-phosphate is converted to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by purine nucleoside phosphorylase.

In the present invention, adenosine deaminase refers to an enzyme that removes an amino group from the adenine moiety of adenosine by hydrolysis to make inosine, and is catalyzes a reaction represented by the following equation:

3) Adenosine deaminase reaction (hydrolysis of amino group)

3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside 3'-amino-2',3'-dideoxyguanosine

As shown in the above reaction, adenosine deaminase hydrolyzes the amino group of the adenine moiety of 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside to prepare 3'-amino-2',3'-dideoxyguanosine.

In the present invention, purine nucleoside phosphorylase and pyrimidine nucleoside phosphorylase are Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase, respectively. In an embodiment of the present invention, the Bacillus stearothermophilus is Bacillus stearothermophilus TH6-2 (FERM BP-2758).

In the present invention, adenosine deaminase is Lactococcus lactis-derived adenosine deaminase. In an embodiment of the present invention, the Lactococcus lactis is Lactococcus lactis KCCM40104.

According to molecular biology and genetic engineering, the molecular biological characteristics and amino acid sequences of the above-described Bacillus stearothermophilus-derived purine nucleoside phosphorylase and/or Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase can be analyzed, and based on the analysis, the genes encoding the proteins can be obtained from the Bacillus stearothermophilus. A recombinant plasmid having inserted therein the gene and a control region necessary for expression can be constructed and introduced into any host, thereby preparing a genetic recombinant strain having the protein expressed therein. Thus, a genetic recombinant strain obtained by introducing the Bacillus stearothermophilus-derived purine nucleoside phosphorylase and/or pyrimidine nucleoside phosphorylase gene into any host also falls within the scope of the present invention.

In addition, the molecular biological characteristics and amino acid sequence of Lactococcus lactis-derived adenosine deaminase can be analyzed, and based on the analysis, the gene encoding the protein can be obtained from the Lactococcus lactis. A recombinant plasmid having inserted therein the gene and a control region necessary for expression can be constructed and introduced into any host, thereby preparing a genetic recombinant strain having the protein expressed therein. Thus, a genetic recombinant strain obtained by introducing the Lactococcus lactis-derived adenosine deaminase gene into any host also falls within the scope of the present invention.

In the present invention, Bacillus stearothermophilus-derived purine nucleoside phosphorylase comprises a purine nucleoside phosphorylase of SEQ ID NO: 1 or its active fragment; Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase comprises a pyrimidine nucleoside phosphorylase of SEQ ID NO: 2 or its active fragment; and Lactococcus lactis-derived adenosine deaminase comprises an adenosine deaminase of SEQ ID NO: 3 or its active fragment.

Bacillus stearothermophilus-derived purine nucleoside phosphorylase may be synthesized from a nucleotide sequence of SEQ ID NO: 4.

Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase may be synthesized from a nucleotide sequence of SEQ ID NO: 5.

Lactococcus lactis-derived adenosine deaminase may be synthesized from a nucleotide sequence of SEQ ID NO: 6.

The above-described recombinant plasmid refers to a genetic construct including essential regulatory elements operably linked to express a gene insert. The control region necessary for expression includes a promoter sequence (including a operator sequence to control transcription), a ribosome-binding sequence (a SD sequence), a transcription termination sequence and the like, and also includes a nucleic acid expression regulatory sequence and a nucleic acid sequence encoding a target protein.

Specific examples of the promoter sequence may be a trp promoter of a tryptophan operon derived from E. coli, a lac promoter of a lactose operon, a promoter derived from λ(lamda) phage, or a gluconatic acid synthase promoter (gnt) derived from Bacillus subtilis, an alkaline protease promoter (apr), a neutral protease promoter (npr), and an α-amylase promoter (amy). Sequences specifically designed and modified, such as a tac promoter, may also be used.

Specific examples of the ribosome-binding sequence include those sequences derived from E. coli or B. subtilis, but are not particularly limited as long as they function within a desirable host such as E. coli, B. subtilis or the like. As an example, a consensus sequence where a sequence of 4 or more consecutive bases is complementary to the 3'-terminal region of a 16S ribosomal RNA may be prepared by DNA synthesis and used.

The transcription termination sequence is not essential, but, if necessary, ones independent of the ρ factor, such as a lipoprotein terminator, a trp operon terminator and the like can be used.

These control regions on the recombinant plasmid are preferably arranged in the order of the promoter sequence, the ribosome-binding sequence, the gene coding for nucleoside phosphorylase or adenosine deaminase, and the transcription termination sequence, from the 5'-terminal on the upstream side.

Examples of the plasmid include, but are not limited to, pFRPT (Korean Patent No. 10-0449639), pBR322, pUC18, Bluescript II SK(+), pKK223-3 or pSC101, which has a region capable of self-replication in E. coli, or pUB110, pTZ4, pC194, ρ11 or φ1-φ105, which have a region capable of self-replication in B. subtilis. In addition, examples of the plasmid capable of self-replication in two or more kinds of hosts include pHV14, TRp7, YEp7, pBS7 and the like.

Examples of any host as described above include, but are not limited to, Escherichia coli, Bacillus sp. strains such as Bacillus subtilis, etc. Preferably, Escherichia coli which is industrially easily available may be used. In an embodiment of the present invention, the host is Escherichia coli JM109.

In the present invention, usable forms of the Bacillus stearothermophilus-derived purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and/or Lactococcus lactis-derived adenosine deaminase include all enzymes themselves, microbial cells having enzymatic activity, treated microbial cells, or immobilized materials thereof, and may be used to perform the reactions. Herein, the microbial cells may be wet microbial cells isolated by centrifugation, or freeze-dried microbial cells. As used herein, the term “treated microbial cells” is meant to include, for example, acetone-dried microbial cells, or microbial cell lysates prepared by mechanical disruption, ultrasonic disruption, freezing-thawing treatment, pressurization-depressurization treatment, osmotic pressure treatment, self-digestion, cell wall degradation, surfactant treatment, etc. In addition, the treated microbial cells, if necessary, include treated microbial cells repeatedly purified by ammonium sulfate precipitation or acetone precipitation, column chromatography.

In one embodiment of the present invention, the present inventors inserted the Bacillus stearothermophilus-derived purine nucleoside phosphorylase and/or pyrimidine nucleoside phosphorylase gene into the E. coli expression vector pFRPT (Korean Patent No. 0449639), and introduced the expression vector into E. coli JM109, thereby constructing genetic recombinant strains, pFRPT-BPUNP/JM109 and pFRPT-BPYNP/JM109. In addition, in the present invention, the Lactococcus lactis-derived adenosine deaminase gene was inserted into the E. coli expression vector pFRPT (Korean Patent No. 0449639) which was then introduced into E. coli JM109, thereby constructing the genetic recombinant strain pFRPT-LADD/JM109.

Wet microbial cells obtained by culture of the constructed genetic recombinant strains and centrifugation, or dried microbial cells obtained by additional freeze drying of the wet microbial cells, were prepared. The prepared wet microbial cells may be used to produce 3'-amino-2',3'-dideoxyguanosine.

In the present invention, step (a) of preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase, and step (b) of preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase, can efficiently produce 3'-amino-2',3'-dideoxyguanosine by reactions under the following conditions.

In the present invention, the reaction temperature in step (a) of preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase may be below 50°C, preferably 30 to 40°C, more preferably about 40°C. At a high temperature of 50°C or above, it was found that 3-amino-2,3-dideoxyribose-1-phosphate became brown by an amino-carbonyl reaction with the passage of time. This browning reduces the yield of the resulting 3'-amino-2',3'-dideoxyguanosine, and impurities produced by the browning interfere with crystallization of 3'-amino-2',3'-dideoxyguanosine in a purification process. For this reason, the reaction is preferably performed at a reaction temperature of about 40°C.

In the present invention, the reaction pH in step (a) of preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase may be pH 7.5 to 9.5, preferably pH 8.0 to 9.0, more preferably pH 8.0 to 8.5, because the enzymes are more stable as the pH is closer to neutral pH.

In the present invention, the reaction time in step (a) of preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase may vary depending on the amount of enzymes used, but is 24-96 hours, preferably 30-48 hours.

In step (a) of preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase according to the present invention, the reaction of 3'-amino-3'-deoxythymidine and 2,6-diaminopurine is preferably performed at a substrate concentration of 1 M or higher. Namely, the reaction is easily carried out at a substrate of high concentration to provide a preparation method suitable for the development of industrial preparation processes.

As the substrates, 3'-amino-3'-deoxythymidine and 2,6-diaminopurine are preferably used at a molar ratio of 1:1. When the substrates are used at a molar ratio of 1:1, there are advantages in that the waste of raw materials can be reduced and in that purification in a subsequent process can be more easily performed. This reduces the waste of raw materials and facilitates purification in a subsequent process, unlike conventional known methods in which a conversion reaction is performed in a state in which the number of equivalents of a specific substrate is increased.

In the present invention, the reaction in the step of reacting 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase may also be performed in the presence of phosphoric acid or its salt.

In the present invention, the reaction in step (b) of preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase may be performed immediately after the reaction of step (a) without a separation purification process. Namely, without removal of the nucleoside phosphorylases used for conversion of the intermediate 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside or without a separate process for purifying the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside, adenosine deaminase may be added directly to the reaction mixture, and in this case, the reaction process time can be reduced and the overall reaction yield can also be greatly increased. Thus, Lactococcus lactis-derived adenosine deaminase may be added directly to the reactant of step (a) without purification of the reactant.

In the present invention, the reaction pH in step (b) of preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase may be 7.0 to 7.5. To maintain this pH, an aqueous solution of weak acid, for example, an aqueous solution of acetic acid, may be added.

In the present invention, the reaction temperature in step (b) of preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase may be 30 to 50°C, preferably 45°C or lower, more preferably 40°C or lower, even more preferably 30 to 40°C, most preferably about 40°C.

In the present invention, the reaction time in step (b) of preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase may be 24 to 120 hours.

The present invention also provides a method for producing 3'-amino-2',3'-dideoxyguanosine, comprising, after step (b) of preparing 3'-amino-2',3'-dideoxyguanosine, step (c) of removing the sources of purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes, and reaction byproducts by adding an alcohol and a strong base to the reactant of step (b).

The method for preparing 3'-amino-2',3'-dideoxyguanosine according to the present invention can produce 3'-amino-2',3'-dideoxyguanosine in high yield without having to perform purification by ion exchange resin, thereby solving the problem in that the process time is increased by adsorption, desorption and fraction concentration in methods that use ion exchange resin or the like. Thus, the method of the present invention is suitable for industrial mass production. Namely, through the above-described steps, 3'-amino-2',3'-dideoxyguanosine purified with high purity can be prepared in high yield.

In the method for preparing 3'-amino-2',3'-dideoxyguanosine according to the present invention, step (c) of removing the sources of purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes, and reaction byproducts by adding an alcohol and a strong base to the reactant of step (b) can remove the sources of purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes, and reaction byproducts, particularly thymine, at the same time under the following conditions, thereby efficiently producing 3'-amino-2',3'-dideoxyguanosine.

Step (c) of removing the sources of purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes, and reaction byproducts by adding an alcohol and a strong base to the reactant of step (b) is a step of simultaneously removing unreacted substrates remaining after the reaction, thymine and guanine which are the main byproducts produced by the reactions, together with the sources of Bacillus stearothermophilus-derived-purine nucleoside phosphorylase, Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase and Lactococcus lactis-derived adenosine deaminase enzymes.

In step (c) of removing the enzyme sources and the reaction byproducts by adding an alcohol and a strong base to the reactant of step (b), in order to remove microbial cells used as the enzyme sources, the microbial cells may generally be filtered out using ultrafiltration (UF), membrane filter (MF) filtration, continuous centrifugation, or celite filtration. Preferably, celite filtration may be used.

The filtration is preferably performed in a state in which materials except for the enzyme sources are dissolved in a solvent. Because conventional nucleosides have high solubility in an aqueous solution, a strong base is preferably added after enzymatic conversion to completely remove nucleosides and bases except for microbial cells, followed by removal of the microbial cells by filtration.

Meanwhile, unlike nucleosides and other bases, thymine was found to have a very low solubility in a solution of a strong base in an alcohol, and thus when the reaction solution is treated with an alcoholic suspension of a base, byproducts such as thymine can also be removed.

Preferably, the reactant of the step of preparing 3'-amino-2',3'-dideoxyguanosine may be treated with a solution of a strong base in an alcohol together with celite to thereby remove the enzyme sources and thymine from the reaction solution. Simultaneous removal of thymine and the enzyme sources has the advantage of simplifying the process, and also has an advantage over the process of removing only the microbial cells in that thymine captures the microbial cells to improve the filtration property to thereby reduce the separation process time.

The strong base that is used in the present invention may be any one or more selected from among sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, and the alcohol that is used in the present invention may be selected from among lower alcohols having 1 to 4 carbon atoms, preferably methyl alcohol, ethyl alcohol, 1-propyl alcohol, and 2-propyl alcohol. Preferably, an alcoholic suspension of a strong base, which is used in the present invention, may comprise methyl alcohol in an amount equal to 13 to 15 times the amount of 3'-amino-3'-deoxythymidine used and sodium hydroxide in an amount equal to 0.6 to 0.8 times the amount of 3'-amino-3'-deoxythymidine used.

In step (c) of removing byproducts by adding an alcohol and a strong base to the reactant of step (b), a filtrate from which the byproducts were removed may be neutralized to a pH of 7.5-8.0 by use of hydrochloric acid, and the neutralized filtrate may be hot-stirred and cold-stirred to form a crystalline material. The crystalline material may be filtered, and a first crystalline material with increased purity may be recovered.

The first crystalline material may further be treated with purified and basic β-charcoal in order to further increase the purity thereof. In a 8 to 12 N aqueous solution of sodium hydroxide in purified water used in an amount equal to 15 to 20 times the amount of 3'-amino-3'-deoxythymidine added, basic β-charcoal may be added to the first crystalline material in an amount equal to 0.05 to 0.3 times the amount of 3'-amino-3'-deoxythymidine added, followed by stirring at a temperature of 70 to 80°C and filtration.

Through this purification process, the content of guanine in byproducts is greatly reduced.

The above crystallization step may be repeated in order to produce 3'-amino-2',3'-dideoxyguanosine with high purity, and a filtration process using a 0.2 μm membrane (MF) filter may be added between the crystallization steps to remove impurities incorporated during the process and microbial cell-derived water-soluble protein aggregates.

The method for preparing 3'-amino-2',3'-dideoxyguanosine according to the present invention shows a high rate of conversion to 3'-amino-2',3'-dideoxyguanosine by use of Bacillus stearothermophilus-derived nucleoside phosphorylases and Lactococcus lactis-derived adenosine deaminase, and thus can produce 3'-amino-2',3'-dideoxyguanosine in high yield and produce 3'-amino-2',3'-dideoxyguanosine with high purity without having to perform purification by ion exchange resin. Therefore, the method of the present invention can produce a large amount of 3'-amino-2',3'-dideoxyguanosine in an economical and efficient manner.

FIG. 1 shows a process for preparing 3'-amino-2',3'-dideoxyguanosine according to the present invention.

FIG. 2 shows the structure of a pFRPT-BPUNP expression vector prepared according to the present invention.

FIG. 3 shows the structure of a pFRPT-BPYNP expression vector prepared according to the present invention.

FIG. 4 shows the structure of a pFRPT-LADD expression vector prepared according to the present invention.

FIG. 5 shows the conversion rate over time according to the enzymatic conversion to 3'-amino-2',3'-dideoxyguanosine in the present invention.

FIG. 6 shows the results of HPLC analysis performed after enzymatic conversion to 3'-amino-2',3'-dideoxyguanosine in the present invention.

FIG. 7 shows the results of HPLC analysis of a substance recovered after enzymatic conversion to 3'-amino-2',3'-dideoxyguanosine and final purification in the present invention.

Hereinafter, the present invention will be described in further detail with reference to examples. It is to be understood, however, that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example 1: Preparation of Strain Expressing Bacillus stearothermophilus-Derived Purine Nucleoside Phosphorylase

A transformed E. coli strain overexpressing Bacillus stearothermophilus-derived purine nucleoside phosphorylase (BPUNP) to be used for transglycosylation in a process for preparation of 3'-amino-2',3'-dideoxyguanosine was prepared in the following manner.

The synthesis of a 705 bp oligonucleotide corresponding to the gene nucleotide sequence (nucleotides 619-1323, SEQ ID NO: 4) of Bacillus stearothermophilus TH 6-2 (FERM BP-2758) and cloning into pUC57 were performed by Macrogen Co., Ltd. (Korea, www.macrogen.com) to obtain pUC57-BPUNP. In addition, for cloning into an expression vector, PCR primers (SEQ ID NOs: 7 and 8) were designed as follows and prepared by Bionics Co., Ltd (Korea, www.bionicsro.co.kr).

Table 1: Primer sequences for BPUNP synthesis

Using the pUC57-BPUNP as a template, a PCR reaction was performed in the presence of 200 μM of dNTP, 20 pmol of primer, 1x Taq DNA polymerase buffer and 2.5 U of Taq DNA polymerase (TaKaRa Ex Taq, cat. # RR001A, TAKARA, Japan, www.takara-bio.com) for 30 cycles, each consisting of 30 sec at 94°C, 1 min at 50°C and 1 min at 72°C. As a result, amplified 723 bp PCR product was confirmed by agarose gel electrophoresis, and purified using a Gel Extraction Kit (QIAquick Gel Extraction Kit, cat. # 28704, Qiagen, Germany, www.qiagen.com). The purified DNA fragment was ligated into a pGEM-T easy vector (pGEM-T easy vector system II, cat. # A1380, Promega, USA, www.promega.com), and then transformed into JM109 E. coli cells (included in pGEM-T easy vector system II). From the resulting E. coli colony, a clone containing the desired plasmid was selected and named “pGEM-BPUNP/JM109”. The pGEM-BPUNP/JM109 strain was inoculated into 3 ml of the medium shown in Table 2 below and was cultured overnight at 37°C, 200 rpm and pH 7, followed by centrifugation to harvest cells. Using a Plasmid Miniprep Kit (Dyne Plasmid Miniprep Kit, cat. # A510, Dynebio, Korea, www.dynebio.co.kr), pGEM-BPUNP was isolated.

Table 2: Components of medium for culture of pGEM-BPUNP/JM109 strain

In order to insert the Bacillus stearothermophilus-derived purine nucleoside phosphorylase prepared as described above into the E. coli expression vector pFRPT (Korean Patent No. 0449639), 10 ug of pFRPT was digested in 20 ul of a reaction solution containing 10 U of NdeI (cat. # 1161A, TAKARA, Japan, www.takara-bio.com) and 10 U of XbaI (cat. # 1093A, TAKARA, Japan, www.takara-bio.com), and the digested plasmid was analyzed by agarose gel electrophoresis, and a 6.45 kbp fragment was purified using a gel extraction kit. Meanwhile, 10 ug of pGEM-BPUNP was digested in 20 ㎕ of a reaction solution containing 10 U of NdeI and 10 U of XbaI, and analyzed by agarose gel electrophoresis as described above, and a 716 bp BPUNP DNA fragment was purified using a gel extraction kit.

The two DNA fragments obtained as described above were reacted in a reaction solution containing 3 U of ligase (T4 DNA ligase, cat. # 2011A, TAKARA, Japan, www.takara-bio.com) and 1X ligase buffer at 16°C for 18 hours. JM109 E. coli cells were transformed with the reaction solution and cultured, and from the resulting E. coli colonies, a plasmid was extracted. The plasmid having the desired DNA fragment inserted therein was named “pFRPT-BPUNP”. FIG. 2 schematically shows the plasmid. The transformed strain obtained as described above was named “pFRPT-BPUNP/JM109”.

Example 2: Preparation of Strain Expressing Bacillus stearothermophilus-derived Pyrimidine Nucleoside Phosphorylase

A transformed E. coli strain overexpressing Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase (BPYNP) to be used for transglycosylation in a process for preparation of 3'-amino-2',3'-dideoxyguanosine was prepared in the following manner.

The synthesis of a 1302 bp oligonucleotide corresponding to the gene nucleotide sequence (nucleotides 138-1439, SEQ ID NO: 5) of Bacillus stearothermophilus TH 6-2 (FERM BP-2758) and cloning into pUC57 were performed by Macrogen Co., Ltd. (Korea, www.macrogen.com) to obtain pUC57-BPYNP. In addition, for cloning into an expression vector, PCR primers (SEQ ID NOs: 9 and 10) were designed as follows and prepared by Bionics Co., Ltd (Korea, www.bionicsro.co.kr).

Table 3: Primer sequences for BPYNP synthesis

Using the pUC57-BPYNP as a template, a PCR reaction was performed in the presence of 200 μM of dNTP, 20 pmol of primer, 1x Taq DNA polymerase buffer and 2.5 U of Taq DNA polymerase for 30 cycles, each consisting of 1 min at 94°C, 1 min at 55°C and 2 min at 72°C. As a result, amplified 1.3 kbp PCR product was confirmed by agarose gel electrophoresis, and purified using a Gel Extraction Kit. The purified DNA fragment was ligated into a pGEM-T easy vector, and then transformed into JM109 E. coli cells. Among the resulting E. coli colony, a clone containing the desired plasmid was selected and named “pGEM-BPYNP/JM109”. The pGEM-BPYNP/JM109 strain was inoculated into 3 ml of the medium shown in Table 2 above and was cultured overnight at 37°C, 200 rpm and pH 7, followed by centrifugation to harvest cells. Using a Plasmid Miniprep Kit, pGEM-BPYNP was isolated from the harvested cells.

In order to insert the Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase prepared as described above into the E. coli expression vector pFRPT, 10 ug of pFRPT was digested in 20 ul of a reaction solution containing 10 U of NdeI and 10 U of HindIII (cat. # 1060A, TAKARA, Japan, www.takara-bio.com), and the digested plasmid was analyzed by agarose gel electrophoresis, and a 6.45 kbp fragment was purified using a gel extraction kit. Meanwhile, 10 ug of pGEM-BPYNP was digested in 20 ul of a reaction solution containing 10 U of NdeI and 10 U of HindIII, and analyzed by agarose gel electrophoresis as described above, and a 1.3 kbp BPYNP DNA fragment was purified using a gel extraction kit.

The two DNA fragments obtained as described above were reacted in a reaction solution containing 3 U of ligase and 1X ligase buffer at 16°C for 18 hours. JM109 E. coli cells were transformed with the reaction solution and cultured. From the resulting E. coli colonies, a plasmid was extracted. The plasmid having the desired DNA fragment inserted therein was named “pFRPT-BPYNP”. FIG. 3 schematically shows the plasmid. The transformed strain obtained as described above was named “pFRPT-BPYNP/JM109”.

Example 3: Preparation of Strain Expressing Lactococcus lactis-Derived Adenosine Deaminase

A transformed E. coli strain overexpressing Lactococcus lactis-derived adenosine deaminase (LADD) to be used for a deamination reaction in a process for preparation of 3'-amino-2',3'-dideoxyguanosine was prepared in the following manner.

A Lactococcus lactis strain (obtained from the Korea culture center of microorganisms, KCCM40104) was inoculated into 50 ml TSB (BactoTM Tryptic Soy Broth, cat. # 211825, BD, USA, www.bd.com) medium, and cultured overnight at 30°C, followed by centrifugation to harvest cells. From the harvested cells, genomic DNA was isolated using a genome purification kit (cat. # A1120, Promega, USA, www.promega.com), and used as a PCR template.

AS PCR primers, oligonucleotides (SEQ ID NOs: 11 and 12) for synthesizing a sequence corresponding to the nucleotide sequence of Lactococcus lactis-derived adenosine deaminase (nucleotides 287447-288505 of Genbank Accession Number NC_002662, SEQ ID NO: 6 (1059 bp)) were prepared as follows and synthesized by Bionics Co., Ltd.

Table 4: Primer sequences for LADD synthesis

Using the genomic DNA of Lactococcus as a template, PCR was performed in the presence of 200 μM of dNTP, 30 pmol of primer, 1x Taq DNA polymerase buffer and 2.5 U of Taq DNA polymerase for 30 cycles, each consisting of 1 min at 94°C, 1 min at 50°C and 1.5 min at 72°C. As a result, amplified 1078 bp PCR product was confirmed by agarose gel electrophoresis, and purified using a Gel Extraction Kit. Using a pGEM-T easy vector, the purified DNA fragment was ligated into a pGEM-T easy vector, and then transformed into JM109 E. coli cells. From the resulting E. coli colony, a clone containing the desired plasmid was selected and named “pGEM-LADD/JM109”. The pGEM-LADD/JM109 strain was inoculated into 3 ml of the medium shown in Table 2 above and was cultured overnight at 37°C, 200 rpm and pH 7, followed by centrifugation to harvest cells. Using a plasmid purification kit, pGEM-LADD was isolated from the harvested cells.

In addition, for overexpression of the enzyme protein, pGEM-LADD was digested with BamHI (cat. # 1010A, TAKARA, Japan, www.takara-bio.com) and HindIII, and ligated into the plasmid expression vector pQE31 (Qiagen, Germany, www.qiagen.com) digested with BamHI and HindIII. The resulting construct was transformed into JM109 E. coli cells, and the plasmid having the desired DNA fragment inserted therein was named “pQE31-LADD”.

Thereafter, in order to insert the Lactococcus lactis-derived adenosine deaminase gene into the E. coli expression vector pFRPT, an oligonucleotide of SEQ ID NO: 13, which is an additional PCR primer based on the nucleotide sequence of pQE31-LADD, was prepared by Bionics Co., Ltd., and used together with the primer of SEQ ID NO: 12.

Using the pQE31-LADD plasmid as a template, a PCR reaction was performed in the presence of 200 μM of dNTP, 30 pmol of primer, 1x Taq DNA polymerase buffer and 2.5 U of Taq DNA polymerase for 30 cycles, each consisting of 1 min at 94°C, 1 min at 50°C and 1.5 min at 72°C. As a result, amplified 1093 bp PCR product was confirmed by agarose gel electrophoresis, and purified using a gel extraction kit. Then, 10 ㎍ of pFRPT was digested in 20 ㎕ of a reaction solution containing 10 U of BglII (cat. # 1021A, TAKARA, Japan, www.takara-bio.com) and 10 U of HindIII. The digested plasmid was analyzed by agarose gel electrophoresis, and a 6.45 kbp fragment was purified using a gel extraction kit.

Meanwhile, 10 ㎍ of the PCR product obtained using the primers of SEQ ID NOs: 13 and 12 was digested in 20 ㎕ of a reaction solution containing 10 U of BglII and 10 U of HindIII, and was analyzed by agarose gel electrophoresis, and a 1093 bp Lactococcus lactis-derived adenosine deaminase DNA fragment was purified using a gel extraction kit. The two DNA fragments obtained as described above were reacted in a reaction solution containing 3 U of ligase and 1X ligase buffer at 16°C for 18 hours. JM109 E. coli cells were transformed with the reaction solution, and then cultured. From the resulting E. coli colony, a plasmid was extracted. The plasmid having the desired DNA fragment inserted therein was named “pFRPT-LADD”, and FIG. 4 schematically shows the plasmid pFRPT-LADD. The transformed strain obtained as described above was named “pFRPT-LADD/JM109”.

Example 4: Preparation of pFRPT-BPUNP/JM109 Wet Cells

For preparation of pFRPT-BPUNP/JM109 wet cells, the strain was cultured using the medium composition shown in Table 5 below.

Table 5: Components of medium for culture of pFRPT-BPUNP/JM109

pFRPT-BPUNP/JM109 was inoculated into a 250 ml Erlenmeyer flask containing 25 ml of the medium shown in Table 5 above, and was shake-cultured overnight at 37°C and 240 rpm. 2 ml of the resulting culture was aseptically inoculated into the 200 ml medium of Table 5 in a 1 L Erlenmeyer flask, and was shake-cultured at 37°C and 240 rpm. When an absorbance of 0.8 was reached, IPTG (isopropyl-1-thio-β-D-galactopyranoside, Carbosynth) was added to a concentration of 1 mM. After 3 hours of additional shaking culture, the resulting culture was centrifuged at 8000 rpm for 10 minutes and washed with 20 ml of 10 mM phosphate buffer. Through this procedure, the source of purine nucleoside phosphorylase enzyme was obtained.

The unit activity of Bacillus stearothermophilus-derived purine nucleoside phosphorylase was calculated as follows:

1) Reaction equation

Guanosine + phosphate guanine + ribose-1-phosphate

2) Activity calculation

U = number of moles of quinine (μmol) / reaction time (min)

Example 5: Preparation of pFRPT-BPYNP/JM109 Wet Cells

For preparation of pFRPT-BPYNP/JM109 wet cells, the strain was cultured using the medium shown in Table 5 above.

pFRPT-BPYNP/JM109 was inoculated into a 250 ml Erlenmeyer flask containing 25 ml of the medium shown in Table 5 above, and was shake-cultured overnight at 37°C and 240 rpm. 2 ml of the resulting culture was aseptically inoculated into the 200 ml medium of Table 5 in a 1 L Erlenmeyer flask, and was shake-cultured at 37°C and 240 rpm. When an absorbance of 0.8 was reached, IPTG (isopropyl-1-thio-β-D-galactopyranoside, Carbosynth) was added to a concentration of 1 mM. After 3 hours of additional shaking culture, the resulting culture was centrifuged at 8000 rpm for 10 minutes, and washed with 20 ml of 10 mM phosphate buffer. Through this procedure, the source of pyrimidine nucleoside phosphorylase enzyme was obtained.

The unit activity of Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase was calculated as follows:

1) Reaction equation

5-methyl uridine + phosphate thymine + ribose-1-phosphate

2) Activity calculation

U = number of moles of thymine (μmol) / reaction time (min)

Example 6: Preparation of pFRPT-LADD/JM109 Wet Cells

For preparation of pFRPT-LADD/JM109 wet cells, the strain was cultured using the medium shown in Table 5 above.

pFRPT-LADD/JM109 was inoculated into a 250 ml Erlenmeyer flask containing 25 ml of the medium shown in Table 5 above, and was shake-cultured overnight at 37°C and 240 rpm. 2 ml of the resulting culture was aseptically inoculated into the 200 ml medium of Table 5 in a 1 L Erlenmeyer flask, and was shake-cultured at 37°C and 240 rpm. When an absorbance of 0.8 was reached, IPTG was added to a concentration of 1 mM. After 3 hours of additional shaking culture, the resulting culture was centrifuged at 8000 rpm for 10 minutes, and washed with 20 ml of 10 mM phosphate buffer. Through this procedure, the source of adenosine deaminase enzyme was obtained.

The unit activity of adenosine deaminase was calculated as follows:

1) Reaction equation

2,6-diaminopurine-2'-deoxyriboside 2'-deoxyguanine

2) Activity calculation

U = number of moles of 2'-deoxyguanine (μmol) / reaction time (min)

Example 7: Analysis of Enzymatic Conversion to 3'-Amino-2',3'-Dideoxy-2,6-Diaminopurineriboside at Varying Reaction Temperatures

As a precursor for synthesis of 3'-amino-2',3'-dideoxyguanosine, 3'-amino-3'-deoxythymidine (ATMD) was synthesized. To synthesize 3'-amino-3'-deoxythymidine, 1 kg of 3'-azido-3'-deoxythymidine (AZT, 3.74 mol) was stirred together with 7.8 L of acetonitrile. 1.17 kg of triphenylphosphine (4.45 mol) was added thereto, followed by stirring at room temperature for 4 hours. Then, 1 L of distilled water was added to the stirred mixture, which was then stirred at room temperature for 4 hours and concentrated under reduced pressure, after which 2 L of methanol was added thereto. The resulting mixture was stirred at room temperature for 8 hours, and then filtered to collect crystals, thereby obtaining 0.79 kg of 3'-amino-3'-deoxythymidine (3.27 mol; a molar yield of 87.4% relative to AZT).

To a substrate solution containing 17.42 g of 2,6-diaminopurine (DAP, 2.32 M), 20 g of the synthesized 3'-amino-3'-deoxythymidine (ATMD, 1.66 M), 50 ml of purified water and 0.8 g of sodium phosphate monobasic (0.134 M), 1.7 g (600 U) of pFRPT-BPUNP/JM109 wet cells and 6.3 g (4400 U) of pFRPT-BPYNP/JM109 wet cells were added, and the mixture was shake-stirred at varying temperatures of 40°C, 50°C and 60°C for 72 hours. Analysis after the reaction was performed under the following conditions: high-performance liquid chromatography column: Inertsil ODS-3 (5 μm; 4.6 mm diameter; 150 mm length; GL Science); mobile phase: 10 mM sodium phosphate buffer (pH 8.0) containing 4% methanol; detection: UV absorption wavelength of 254 nm.

The rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside (ADDAP) was calculated as follows:

ADDAP conversion rate (%)=(ADDAP HPLC area% X 100) ÷ (ADDAP HPLC area% + DAP HPLC area%)

The rates of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside (ADDAP) are shown in Table 6 below.

Table 6: Rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside

As can be seen in Table 6 above, at 40°C, the highest conversion rate was shown, and at a temperature of 50°C or higher, the color of the reaction solution changed to brown or reddish brown, and 3'-amino-3'-deoxythymidine was decomposed in an amount considerably larger than that of unreacted 2,6-diaminopurine. Thus, a temperature of about 40°C was determined to be preferable.

Example 8: Analysis of Enzymatic Conversion to 3'-Amino-2',3'-Dideoxy-2,6-Diaminopurineriboside at Varying Molar Ratios between 3'-Amino-3'-Deoxythymidine and 2,6-Diaminopurine

Base on 10 g (41.5 mmol) of 3'-amino-3'-deoxythymidine, 2,6-diaminopurine was added in varying amounts of 8.71 g (58.0 mmol, 1.4 equivalents), 7.49 g (49.9 mmol, 1.2 equivalents) and 6.25 g (41.6 mmol, 1 equivalent). Then, each of the mixtures was suspended in 25 ml of 10 mM sodium phosphate monobasic solution, and 0.86 g (300 U) of pFRPT-BPUNP/JM109 wet cells and 3.14 g (2200 U) of pFRPT-BPYNP/JM109 wet cells were added thereto, followed by shake-stirring at 40°C for 5 days. The rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside in each reaction solution was analyzed by HPLC in the same manner as described in Example 7, and the results of the analysis are shown in Table 7 below.

Table 7: Rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside

As can be seen in Table 7 above, when enzymatic conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was performed using Bacillus stearothermophilus-derived nucleoside phosphorylases, the conversion rate showed a tendency to increase as the number of equivalents of 2,6-diaminopurine per equivalent of 3'-amino-3'-deoxythymidine decreased. In addition, the absolute value of 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside produced was also high.

Namely, in the method of the present invention, the molar ratio between 3'-amino-3'-deoxythymidine and 2,6-diaminopurine was set at 1:1 in order to minimize the production of reaction byproducts.

Example 9: Analysis of Enzymatic Conversion to 3'-Amino-2',3'-Dideoxy-2,6-Diaminopurineriboside at Varying pHs

To a substrate solution containing 12.5 g of 2,6-diaminopurine (83.2 mmol), 20 g of 3'-amino-3'-deoxythymidine (82.9 mmol), 50 ml of purified water and 0.06 g of sodium phosphate monobasic (0.5 mmol), 1.7 g (600 U) of pFRPT-BPUNP/JM109 wet cells and 6.3 g (4400 U) of pFRPT-BPYNP/JM109 wet cells were added. The pH of the reaction mixture was adjusted to 7.6, 8.0 and 8.8, followed by shake-stirring at 40°C for 24 hours. The rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside in each reaction solution was analyzed by HPLC in the same manner as described in Example 7, and the results of the analysis are shown in Table 8 below.

Table 8: Rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside

As can be seen in Table 8 above, when enzymatic conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was performed using Bacillus stearothermophilus-derived nucleoside phosphorylases, the conversion rate showed a tendency to increase as the pH increased. Thus, it was found that the preferred pH of the reaction solution is between 8.0 and 9.0, and the enzymes were more stable as the pH was closer to neutral pH. Thus, a pH ranging from 8.0 to 8.5 was determined to be preferable.

Example 10: Analysis of Enzymatic Conversion to 3'-Amino-2',3'-Dideoxy-2,6-Diaminopurineriboside at Varying Substrate Concentrations

To 12.5 g of 2,6-diaminopurine (83.2 mmol), 20 g of 3'-amino-3'-deoxythymidine (82.9 mmol) and 0.06 g of sodium phosphate monobasic (0.5 mmol), 50 ml (1.7 M substrate concentration) and 85 ml (1.0 M substrate concentration) of purified water was added to prepare substrate solutions, respectively. To 1.7 g (600 U) of pFRPT-BPUNP/JM109 wet cells and 6.3 g (4400 U) of pFRPT-BPYNP/JM109 wet cells were added, and then the pH of each reaction solution was adjusted to 8.0, followed by shake-stirring at 40°C for 24 hours.

The rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside in each reaction solution was analyzed by HPLC in the same manner as described in Example 7 above, and the results of the analysis are shown in Table 9 below.

Table 9: Rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside

As can be seen in Table 9 above, when enzymatic conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was performed using Bacillus stearothermophilus-derived nucleoside phosphorylases, the conversion rate increased as the substrate concentration increased. In addition, at a substrate concentration of 1.0 M or higher, the reaction for conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by Bacillus stearothermophilus-derived nucleoside phosphorylases easily proceeded.

Example 11: Analysis of Enzymatic Conversion to 3'-Amino-2',3'-Dideoxyguanosine (ADG) by Addition of Lactococcus lactis-Derived Adenosine Deaminase to Reaction Solution

To a substrate solution containing 12.5 g of 2,6-diaminopurine (83.2 mmol), 20 g of 3'-amino-3'-deoxythymidine (82.9 mmol), 50 ml of purified water and 0.06 g sodium phosphate monobasic (0.5 mmol), 1.7 g (600 U) of pFRPT-BPUNP/JM109 wet cells and 6.3 g (4400 U) of pFRPT-BPYNP/JM109 wet cells were added, and the mixture was adjusted to a pH of 8.0, followed by shake-stirring at 40°C for 48 hours. The analysis of the reaction solution by HPLC indicated that the rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was 70%. After the rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was confirmed to reach 70%, 20 ml of purified water was added to the reaction solution, and 0.4 g (1200 U) of pFRPT-LADD/JM109 wet cells were added thereto. Next, the reaction solution was shake-stirred at 40°C for 90 hours while the pH was maintained at 7.0-7.5 by use of a 50% aqueous solution of acetic acid. At this time, the reaction rate was 99.65%.

The reaction rate was calculated as follows.

3'-amino-2',3'-dideoxyguanosine reaction rate (%)=[(ADG HPLC area% + ADDAP HPLC area%) X 100] ÷ (ADG HPLC area% + ADDAP HPLC area% + DAP HPLC area%)

It was found that enzymatic conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside could be achieved by transglycosylation using Bacillus stearothermophilus-derived nucleoside phosphorylases, and then enzymatic conversion from 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside to 3'-amino-2',3'-dideoxyguanosine could be achieved by adding Lactococcus lactis-derived adenosine deaminase directly to the reaction solution of the first enzymatic conversion reaction. Namely, it was found that it is possible to produce 3'-amino-2',3'-dideoxyguanosine from the same reaction solution by deamination using Lactococcus lactis-derived adenosine deaminase without having to remove the Bacillus stearothermophilus-derived nucleoside phosphorylase enzyme sources or without having to purify the intermediate 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside.

Example 12: Removal of Microbial Cells and Thymine

The reaction solution resulting from Example 11 was divided into four equal portions, and varying ratios of sodium hydroxide and methyl alcohol were added to each of the divided portions to perform simultaneous removal of microbial cells and thymine (TMN).

Specifically, sodium hydroxide and methyl alcohol were added to each of the portions in the following amounts: based on the amount of 3'-amino-3'-deoxythymidine added, sodium hydroxide in an amount equal to 0.9 times and methyl alcohol in an amount of 20 times (4.5 g of sodium hydroxide and 100 ml of methyl alcohol); sodium hydroxide in an amount equal to 0.65 times and methyl alcohol in an amount of 20 times (3.25 g of sodium hydroxide and 100 ml of methyl alcohol); sodium hydroxide in an amount equal to 0.65 times and methyl alcohol in an amount of 14 times (3.25 g of sodium hydroxide and 70 ml of methyl alcohol); and sodium hydroxide in an amount equal to 0.65 times and methyl alcohol in an amount of 10 times (3.25 g of sodium hydroxide and 50 ml of methyl alcohol). Then, each of the mixtures was stirred at 40°C for 1 hour and cooled slowly, and then maintained at 4°C for 3 hours, followed by filtration under reduced pressure to remove microbial cells and thymine.

Following the removal of microbial cells and thymine, the results of HPLC analysis (Area%) are shown in Table 10 below.

Table 10: Analysis of thymine removal and 3'-amino-2',3'-dideoxyguanosine

It was shown that thymine was removed from all reaction solutions except for the reaction solution in which sodium hydroxide was used in an amount equal to 0.65 times the amount of 3'-amino-3'-deoxythymidine added and methyl alcohol was used in an amount equal to 10 times (3.25 g of sodium hydroxide and 50 ml of methyl alcohol). Particularly, it was shown that, in the case in which sodium hydroxide was used in an amount equal to 0.65 times the amount of 3'-amino-3'-deoxythymidine added and methyl alcohol was used in an amount equal to 14 times, the largest amount of thymine was removed by filtration and the content of 3'-amino-2',3'-dideoxyguanosine was the highest.

Example 13: Analysis of Enzymatic Conversion to 3'-Amino-2',3'-Dideoxyguanosine

To a substrate solution containing 31.15 g of 2,6-diaminopurine (207.39 mmol), 50 g of 3'-amino-3'-deoxythymidine (207.30 mmol), 125 ml of purified water and 0.15 g of sodium phosphate monobasic (1.25 mmol), 4.3 g (1500 U) of pFRPT-BPUNP/JM109 wet cells and 15.7 g (11000 U) of pFRPT-BPYNP/JM109 wet cells were added, and the mixture was adjusted to a pH of 8.0, followed by shake-stirring at 40°C for 48 hours. The analysis of the reaction solution by HPLC indicated that the rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was 72.0%. After the rate of conversion to 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside was confirmed to reach 70% or higher, 50 ml of purified water was added to the reaction solution, and 1 g (3000 U) of pFRPT-LADD/JM109 wet cells were added to the reaction solution, after which the reaction solution was shake-stirred at 40°C for 72 hours while the pH was kept at 7.0-7.5 by use of a 50% aqueous solution of acetic acid. At this time, the reaction rate was 98.5%. The rate of conversion to 3'-amino-2',3'-dideoxyguanosine with time is shown in FIG. 5. As shown in FIG. 5, the reaction rate increased with the passage of time.

In addition, the results of HPLC analysis of the reaction solution are shown in FIG. 6. The HPLC analysis results indicated that 3'-amino-2',3'-dideoxyguanosine was detected together with some byproducts.

Example 14: Isolation and Purification of 3'-Amino-2',3'-Dideoxyguanosine from Reaction Solution

To the reaction solution resulting from Example 13, a solution of 32.5 g of sodium hydroxide in 700 ml of methyl alcohol was added. Then, the reaction solution was stirred at 40°C for 1 hour and cooled slowly, and then cold-stirred at 4°C for 3 hours, followed by celite filtration to remove microbial cells and thymine from the reaction solution. The filtrate from which microbial cells and thymine were removed was adjusted to a pH of 8.1 by use of hydrochloric acid, and then stirred at 75°C for 1 hour and cooled slowly, after which it was stirred at 35°C for 3 hours, followed by filtration to obtain a first crystalline material. 800 ml of purified water was added to the first crystalline material which was then adjusted to a pH of 10 by use of a 10 N aqueous solution of sodium hydroxide, followed by stirring at 75°C for 1 hour. After stirring at 75°C for 1 hour, 5 g of basic β-charcoal was added thereto, followed by additional stirring at 75°C for 1 hour. The stirred material was hot-filtered.

While the filtration was performed, a filtration process using a 0.2 μm membrane was also performed. The filtrate was adjusted to a pH of 7.5 by use of a 50% aqueous solution of hydrochloric acid and concentrated. The concentrated residue was suspended in 800 ml of ethyl alcohol, and the suspension was stirred at 75°C for 2 hours and cooled slowly, and then stirred at 35°C for 3 hours, followed by filtration. The filtrate was dried in a vacuum.

After isolation and purification as described above, HPLC analysis was performed, and the results of the analysis are shown in FIG. 7.

As shown in FIG. 7, 37.9 g (142.3 mmol) of 3'-amino-2',3'-dideoxyguanosine with a HPLC purity of 99.1% was finally recovered, which corresponds to a weight yield of 75.8% and a molar yield of 68.6%, based on the amount of 3'-amino-3'-deoxythymidine added.

Through the above-described results, it was found that the method for preparing 3'-amino-2',3'-dideoxyguanosine according to the present invention is suitable for commercial mass production.

Claims

A method for preparing 3'-amino-2',3'-dideoxyguanosine, comprising the steps of:

(a) preparing 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside by treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase; and

(b) preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase.
The method of claim 1, wherein the Bacillus stearothermophilus-derived purine nucleoside phosphorylase in step (a) comprises an amino acid sequence of SEQ ID NO: 1, the Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase in step (a) comprises an amino acid sequence of SEQ ID NO: 2, and the Lactococcus lactis-derived adenosine deaminase in step (b) comprises an amino acid sequence of SEQ ID NO: 3.
The method of claim 1, wherein step (a) of treating 3'-amino-3'-deoxythymidine and 2,6-diaminopurine with Bacillus stearothermophilus-derived purine nucleoside phosphorylase and Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase is a reaction which is performed below 50°C.
The method of claim 1, wherein the 3'-amino-3'-deoxythymidine and the 2,6-diaminopurine in step (a) are used in a reaction at a molar ratio of 1: 1.
The method of claim 1, wherein step (a) is a step in which the 3'-amino-3'-deoxythymidine and the 2,6-diaminopurine are added at a high concentration of 1M or higher and reacted with each other.
The method of claim 1, wherein step (b) of preparing 3'-amino-2',3'-dideoxyguanosine by treating the 3'-amino-2',3'-dideoxy-2,6-diaminopurineriboside with Lactococcus lactis-derived adenosine deaminase comprises adding the Lactococcus lactis-derived adenosine deaminase directly to a reactant of step (a) without purifying the reactant.
The method of claim 1, wherein the Bacillus stearothermophilus-derived purine nucleoside phosphorylase, the Bacillus stearothermophilus-derived pyrimidine nucleoside phosphorylase and the Lactococcus lactis-derived adenosine deaminase are enzymes overexpressed in E. coli cells or treated E. coli cells, prepared by genetic recombination.
The method of claim 1, further comprising, after step (b) of preparing 3'-amino-2',3'-dideoxyguanosine, step (c) of removing sources of purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes, and reaction byproducts by adding an alcohol and a strong base to a reactant of step (b).
The method of claim 8, wherein the alcohol in step (c) is a lower alcohol having 1 to 4 carbon atoms, and the strong base in step (c) is any one or more selected from among sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide.
The method of claim 8, wherein the sources of the purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes are enzyme sources in microbial cells or treated microbial cells, and the reaction byproducts include thymine.
The method of claim 8, wherein the sources of the purine nucleoside phosphorylase, pyrimidine nucleoside phosphorylase and adenosine deaminase enzymes are enzyme sources in microbial cells or treated microbial cells, and the reaction byproducts include thymine.