CN116200359A - Transaminase mutant and application thereof - Google Patents

Abstract

The invention relates to an application of a transaminase mutant in synthesizing a key chiral intermediate D-4,4' -biphenylalanine of sarcandesartan sodium salt (LCZ 696), belonging to the technical field of biocatalysis synthesis. The mutant is a quadruple mutant with an amino acid sequence shown as SEQ ID NO. 1, the amino acid sequence of the aminotransferase mutant is shown as SEQ ID NO. 3, and the corresponding amino acid sequence is shown as SEQ ID NO. 4. Compared with a wild transaminase female parent, the unit enzyme activity is improved to about 30 times under the condition of ensuring the chiral purity of the product, the method has very high stereoselectivity and conversion rate, can further reduce the industrial production cost of sabobiliprotic and LCZ696, and has good industrial application value.

Description

Transaminase mutant and application thereof

Technical Field

The invention belongs to the technical field of biocatalysis synthesis, and particularly relates to application of a transaminase mutant in synthesis of a key chiral intermediate D-4,4' -biphenylalanine of sarcandesartan sodium salt (LCZ 696).

Background

LCZ696 (trade name entrestro, formula a) is a dual-effect angiotensin receptor enkephalinase (NEP) inhibitor developed by northwest pharmaceuticals in the united states, consisting of Valsartan (Valsartan, formula B) and sabobiril (sacubiril, also known as AHU377, formula C) in a molar ratio of 1:1, and is marketed with FDA approval at 7 months 2015 for the treatment of hypertension and heart failure.

The formula D (D-4, 4' -biphenylalanine) is used as a key chiral intermediate for preparing the sarcandra, and becomes a key factor for restricting the production of the sarcandra (figure 1). Sha Kubi and formula D and its analogues chemical process of preparation have been reported in numerous patents (in WO 2007/083774, WO 2007/083776, WO 2008/031567, WO 2008/083967, WO 2008/120567, WO 2009/090251, WO 2010/081410, WO 2011/035569, WO 2011/088797, WO 2012/025501, WO 2012/025502, WO 2013/026773, WO 2014/032527, WO 2015/024991, WO 2015/037460, CN101362708, CN102260177, CN103483201, CN104557600, CN104725256, CN104725279, CN105017082, CN105061263, CN105085322, CN105152980, CN105168205, CN105198775, CN105237560, CN105330569, CN105481622, CN105566194, CN105601524 and CN 105884656), but these methods still have significant drawbacks such as potentially hazardous reactants or limited stereoselectivity. Thus, there remains a need to devise more optimal preparation methods to provide an inexpensive way to obtain D-4,4 '-biphenylalanine for synthesis, which are suitable for industrial scale production under economically and environmentally more advantageous conditions and to provide D-4,4' -biphenylalanine with high chemical purity and high stereochemical selectivity.

WO 2018/116203 and CN 110088079R) The selective omega-aminotransferase catalyzes 4,4 '-biphenylpyruvic acid (substrate), the substrate conversion rate is close to 100% after 17-18 hours of reaction at 40-45 ℃, and D-4,4' -biphenylalanine with ee value more than 99% is obtained after post-treatment, and the yield is 90%. Exhibit great advantages of biological enzyme catalysis on the synthesis of the chiral compound. However, the transaminase has a long reaction time, which indicates that the catalytic efficiency of the enzyme still has room for improvement. The transaminase of different biological sources is searched, and enzyme molecules are modified by means of a protein engineering method to obtain more efficient transaminase, so that the transaminase is an effort direction for realizing the industrial production of the key chiral intermediate D-4,4' -biphenylalanine of LCZ696 by an enzyme method.

Disclosure of Invention

The invention aims to: aiming at the defects of the existing synthesis method for preparing D-4,4' -biphenylalanine, the preparation process suitable for green chemical industrial production is provided, and the raw material medicine with excellent quality and low cost is further provided for society.

The technical scheme is as follows: the invention is based on screeningMycolicibacteriumagriThe natural transaminase of the strain is a transaminase mutant obtained by directed evolution on the basis, and the transaminase mutant is used for catalyzing 4,4 '-biphenylpyruvic acid to synthesize D-4,4' -biphenylalanine, and the reaction formula is as follows:

wherein: PLP is pyridoxal 5' -phosphate, a coenzyme for transaminases.

The present invention provides an improved transaminase, i.e., a transaminase mutant, which has significantly higher enzymatic activity than the wild-type transaminase.

The technical scheme of the invention is that the aminotransferase mutant is a quadruple mutant of an amino acid sequence shown in SEQ ID NO. 1 (the nucleotide sequence corresponding to the coding gene is SEQ ID NO. 2), and mutation points comprise the following points: the mutation of R at position 60 to G, D at position 72 to A, K at position 196 to N and Q at position 199 to L.

The amino acid sequence of the aminotransferase mutant is as follows: the nucleotide sequence of the corresponding coding gene is shown as SEQ ID NO. 3 and SEQ ID NO. 4.

According to another aspect of the invention there is provided a recombinant plasmid comprising the nucleotide sequence of any of the above-mentioned genes (+), further comprising the plasmids pET-28a (+), pET-28b (+), pET-28c (+), pET-5b (+), pET-15b, pET-24a (+), pET-24c (+), pET-24d (+), pET-25b (+), pET-27b (+), pET-28c (+), pET-29a (+), pET-29b (+), pET-29c (+), pET-30b (+), pET-30c (+), pET-30 Xa/LIC, pET-30 EK/LIC, pET-31b (+), pET-32c, pET-32 EK/LIC, pET-32/LIC, pET-33b (+), pET-37b, pET-39b, pET-40b, pET-42, pET-44b (+), pET-43 b (+), pET-43, and/4 b (+), pET-43 pET-44 EK/LIC, pET-45b (+), pET-46 EK/LIC, pET-47b (+), pET-48b (+), pET-49b (+), pET-51b (+), pET-52b (+), pQE30, pQE31, pQE32, pQE40, pBV220, pBV221, pCold-GST or pTrcHisC.

According to a further aspect of the present invention there is provided a host cell comprising any of the recombinant plasmids described above, and the host cell comprises a prokaryotic cell, preferably an E.coli BL21 (DE 3) cell, or a eukaryotic cell.

According to another aspect of the invention there is also provided the use of a transaminase mutant in the preparation of D-4,4' -biphenylalanine, comprising: in the presence of transaminase mutant, 4 '-biphenylpyruvate is used as a substrate, and D-4,4' -biphenylalanine is obtained through asymmetric transamination.

Specifically, the transaminase mutant is applied to the preparation of D-4,4' -biphenylalanine, phosphate buffer solution is used for controlling pH to be in the range of 7.5-9.5, preferably 8.0-9.0 in the catalytic ammonia conversion reaction, and the pH is basically stable in the reaction process without additional acid-base solution adjustment.

In the reaction process, the pH is lower than 7.5 or higher than 9.5, the enzyme catalysis reaction speed is obviously reduced, and even the substrate cannot be reacted.

In particular, the aminotransferase mutant is applied to the preparation of D-4,4' -biphenylalanine, and the catalytic ammonia transfer reaction temperature is controlled at 25-45 ℃, preferably 30-40 ℃. The reaction temperature is lower than 25 ℃ or higher than 45 ℃, the enzyme catalysis reaction speed is reduced or even the substrate cannot be reacted completely.

Description of the drawings:

FIG. 1A process flow diagram for preparing sabobiqu by chemical synthesis-transaminase catalysis

FIG. 2 is a graph showing the results of protein electrophoresis detection of transaminase mutants in the preferred embodiment 6 of the present invention

FIG. 3 chiral purity HPLC chromatogram of D-4,4' -biphenylalanine

The beneficial effects are that: according to the technical scheme, on the basis of wild type aminotransferase shown in SEQ ID NO. 1 (the nucleotide sequence of the corresponding coding gene is shown in SEQ ID NO. 2), a random mutation molecular biological method is adopted to mutate the maternal gene of the aminotransferase, so that the amino acid sequence of the enzyme is changed, the change of the enzyme structure and the function is realized, and the aminotransferase quadruple mutant with the mutation sites is obtained by a directional screening method. The transaminase mutant is used for catalyzing 4,4 '-biphenylpyruvic acid to synthesize D-4,4' -biphenylalanine, and compared with a wild type transaminase female parent, the unit enzyme activity is improved by about 30 times under the condition of ensuring the chiral purity of the product (example 5). The invention provides a new technical scheme with higher transaminase mutant and substrate conversion efficiency (reaction 4-8 h relative to reaction 17-18 h under the condition of equivalent enzyme dosage) compared with the existing disclosed optimal enzyme catalysis process (patent CN 110088079 enzyme catalysis reaction 18 h substrate conversion rate 100%, e.e. value > 99%), and can further reduce industrial production cost of sabobiqu and LCZ 696.

The specific embodiment is as follows: the invention will be further described with reference to the following examples of embodiments, but the scope of the invention is not limited thereto:

example 1: obtainingMycolicibacteriumagriWild transaminase female parent recombinant plasmid of strain

Obtained through NCBI Protier databaseMycolicibacteriumagriThe amino acid sequence (NCBI Reference Sequence:WP_ 097938638.1,SEQ ID NO:1) and gene sequence (NCBI Reference Sequence:NZ_PDCP 01000006.1, base sequence position 40721~41737,SEQ ID NO:2) of the transaminase parent of the strain were codon optimized and the service provider was entrusted to the artificial synthesis of the full-length gene into the pET28a (+) expression plasmid, after which competent cells of E.coli BL21 (DE 3) were transformed, plated on LB agar plates containing 50 mg/L kanamycin sulfate, and cultured overnight at 37 ℃. Several single colonies were selected to LB medium (containing 50 mg/L kanamycin sulfate), and after overnight incubation at 37℃the recombinant plasmid was extracted using a plasmid miniprep kit, and PCR and sequencing verification was performed to obtain the recombinant plasmid of the wild type Rhine enzyme female parent.

Example 2: random mutation of wild type transaminase parent Gene

According to the embodiment 1, to containMycolicibacteriumagriRecombinant plasmid of transaminase female parent coding gene of strain is used as template, and two-end primers (table 1) are designed and synthesized by using Primer 5.0 according to transaminase female parent coding gene, error-prone PCR technique (material and concentration are shown in table 2, reaction condition is shown in table 3) is used to obtain linear gene fragment containing lots of base mutations, and these PCR products and pET28a (+) expression plasmid are respectively undergone the processes of enzyme digestion, gel cutting recovery, connection and conversion of colibacillus BL21 (DE 3) inductanceThe cells were plated on LB agar plates containing 50 mg/L kanamycin sulfate and cultured overnight at 37 ℃. Details are shown in tables 1-3.

Example 3: cloning and expression of transaminase mutants

In order to facilitate cloning, expression and identification of transaminase mutants, compatible restriction enzyme sites are designed at the 5 'and 3' ends of the gene, and can be usedNco IAndXho Irestriction enzymes respectively enzyme cutting target gene and pET28a (+) (other expression plasmids which can express protein in colibacillus can be used) simultaneously, recovering DNA cutting gel, connecting the recovered target gene and larger fragment of plasmid by T4 DNA ligase, transforming the connection product into competent cells of colibacillus BL21 (DE 3), coating the transformed competent cells on LB agar plate containing 50 mg/L kanamycin sulfate, and culturing at 37 ℃ overnight.

Single colonies growing on the culture dish are selected and inoculated into LB liquid medium containing 50 mg/L kanamycin sulfate, shaking culture is carried out at 37 ℃ for overnight, plasmid extraction, PCR identification and double enzyme digestion identification are carried out on the collected thalli, then the correct recombinant plasmid is named as pET28a (+) -A-N, and the escherichia coli containing the correct recombinant plasmid is subjected to subsequent induced expression. Transferring the bacterial liquid into 500 mL LB liquid medium containing 100 mg/L ampicillin, shaking culturing at 37deg.C to OD ₆₀₀ When the bacterial liquid is=0.6-0.8, IPTG is added to the final concentration of 0.05-0.5 mM respectively, induced expression is carried out at 22-25 ℃ for 12-16 h, bacterial liquid is taken out, 6000 Xg is centrifuged for 20 min, and bacterial cells are collected and frozen at-20 ℃ for standby.

Example 4: preliminary screening of transaminase mutants

According to the description of example 2 and example 3, the above-mentioned LB agar medium was inoculated with a single colony in a 48-well plate, 1mL LB medium containing 50 mg/L kanamycin sulfate was previously added to each well, 3 h of the culture was shake-cultured at 37℃and 220 rpm, a certain amount of inducer isopropyl-. Beta. -D-thiogalactoside (IPTG, final concentration: 0.15 mM) was added, the culture was induced at 25℃and 220 rpm for 15 hours, 6000 Xg was centrifuged for 20 minutes to collect bacterial cells, the supernatant was removed by centrifugation, and then the bacterial cells were resuspended by using 0.5mL potassium phosphate buffer (100 mM, pH 8.5), 0.1 mL of 4,4' -bipyruvate solution (2 mM), 0.2 mL of 70% isopropylamine solution, 0.2 mL of PLP solution (2 mM), the total reaction volume was 1.0mL of methanol was added for 22 hours at 40℃to terminate the reaction, and after shaking, the supernatant was removed and the conversion was detected by centrifugation.

Example 5: rescreening of transaminase mutants

(1) Preparation of transaminase mutant enzyme solutions

The mutant strain with higher enzyme activity than the female parent in example 4 is inoculated in 10-20 bottles of LB culture medium containing 100 mg/L ampicillin in 500-mL respectively in an inoculation amount of 0.1%, the culture is carried out for 5-6 hours at 37 ℃ under shaking at 220 rpm, a certain amount of inducer isopropyl-beta-D-thiogalactoside (IPTG, final concentration of 0.1 mM) is added, the culture is induced at 25 ℃ and at 220 rpm for 16 hours, and 6000 Xg is centrifuged for 20 minutes to collect the bacterial body. Using 100 mM potassium phosphate buffer solution (pH 8.5) to crack cell walls of cells of a cell body of 200 g/L whole cell, using a high-pressure homogenizing breaker (800-900 bar), centrifuging the broken liquid at 4 ℃ and 10000 Xg for 30 min to obtain supernatant, namely transaminase mutant crude enzyme liquid.

(2) Reaction of preparing D-4,4 '-biphenylalanine by catalyzing 4,4' -biphenylpyruvic acid with transaminase

The main raw materials of 4,4' -bipyruvate 0.2 g, dipotassium phosphate trihydrate 1.0 g, 50mM (pH 8.5) potassium phosphate buffer 10 mL, 70% isopropylamine solution 1.0mL, 30% tween-20 solution 1.0mL and pyridoxal coenzyme phosphate solution (2 mM) 0.4 mL are added into a 20 mL reaction bottle, the temperature is raised to 35 ℃, 50 mg (0.25 weight) of transaminase mutant enzyme solution is added, 2 mol/L NaOH solution is adopted to adjust the reaction pH to 8.5-9.0, the reaction is ended after 16 hours, and the conversion rate and e.e value are analyzed by HPLC.

Control example: the main materials 4,4' -bipyruvate 0.2 g, dipotassium hydrogen phosphate trihydrate 1.0 g, 50mM (pH 8.5) potassium phosphate buffer 10 mL, 70% isopropylamine solution 1.0mL, 30% tween-20 solution 1.0mL and pyridoxal coenzyme phosphate solution (2 mM) 0.4 mL are respectively added into two 20 mL reaction bottles to be mixed into a reaction system, the temperature is raised to 35 ℃, transaminase female enzyme solutions 50 mg (0.25 wt) and 500 mg (2.50 wt) are respectively added, 2 mol/L NaOH solution is adopted to adjust the reaction pH to 8.5-9.0, the reaction is finished for 16 hours, and the conversion rate and e.e value are analyzed by HPLC.

(3) Measurement of the conversion in the control of the catalytic reaction of transaminases

The reaction system was diluted with solvent [ 0.01mol/L potassium dihydrogen phosphate solution (containing 0.1% phosphoric acid) -acetonitrile (50:50) ] and subjected to membrane filtration followed by HPLC direct sample injection analysis. The HPLC conditions were:

instrument: thermo U3000 system HPLC

Chromatographic column: agilent ZOBAX SB-phenyl,4.6 mm. Times.250 mm,5 μm

Mobile phase: linear gradient elution was performed using 0.01mol/L potassium dihydrogen phosphate solution (pH adjusted to 3.0 with phosphoric acid) as mobile phase A and acetonitrile as mobile phase B, as shown in the following table;

detection wavelength: 255 nm;

flow rate: 1.0 mL/min;

column temperature: 30 ℃;

sample injection volume: 10 mu L.

Conversion calculation formula:

wherein A (P) is the peak area of D-4,4' -biphenylalanine;

a (S) is the peak area of the starting material 4,4' -bipyruvate.

(4) Identification of optical purity of transaminase catalytic products

Taking a proper amount of the product, ultrasonically dissolving and diluting the product by using a solvent to prepare a solution containing about 2mg per 1ml, weighing 1ml, placing the solution into a 5ml centrifuge tube, sequentially adding 0.5ml of borate buffer solution and 0.5ml of FMOC-Cl solution, shaking for 1 minute, then adding 50 mu l of acetic acid, and shaking uniformly.

The HPLC conditions were:

instrument: thermo U3000 system HPLC

Chromatographic column: chiralcel OJ-RH, 4.6mm.times.150mm, 5 μm

Mobile phase: acetonitrile solution of 0.1% trifluoroacetic acid is mobile phase A, and aqueous solution of 0.1% trifluoroacetic acid is mobile phase B

Detection wavelength: 263 nm;

flow rate: 0.7mL/min;

column temperature: 25 ℃;

sample injection volume: 3. Mu.L.

Calculation formula of optical purity of R-type product:

wherein A (R) is the peak area of the target product D-4,4' -biphenylalanine;

a (S) is the peak area of enantiomer L-4,4' -biphenylalanine.

The mutant with catalytic activity superior to that of the female parent is selected for sequencing, mutation sites are analyzed, and the catalytic activity of the tetrad mutant R60G-D72A-K196N-Q199L (SEQ ID NO:3 and the nucleotide sequence corresponding to the coding gene SEQ ID NO: 4) is obviously improved compared with that of the female parent in the scheme, and the e.e. value of the product is not reduced. The re-screening reaction results are shown in Table 4.

Note that: in Table 4 ^* Refers to the mass (g) of each transaminase enzyme solution required for conversion of 1g substrates. 0.25wt means that 0.25 g transaminase mutant enzyme solution is required for conversion of 1g main raw material.

Table 4 results illustrate: the catalytic efficiency of the R60G-D72A-K196N-Q199L tetrad mutant on 4,4' -bipyruvate is about 30 times that of a wild transaminase female parent, and the product has an e.e. value and the female parent can reach 99.9%.

Example 6: preparation of R60G-D72A-K196N-Q199L tetrad mutant enzyme powder

The mutant strain in example 5 was inoculated (500 mL/30 flasks) in LB medium containing 50 mg/L kanamycin sulfate at 37℃and 220 rpm shaking culture for 5-6 h, a certain amount of inducer isopropyl-. Beta. -D-thiogalactoside (IPTG, final concentration of 0.15 mM) was added, the culture was induced at 25℃and 220 rpm for 16 h, and the cells were collected by centrifugation at 6000 Xg. And (2) uniformly re-suspending 90-100 g of the obtained bacterial cells by using 200 mL of 50mM potassium phosphate buffer solution (pH 8.5), crushing the cells by using a high-pressure homogenizer (800-900 bar), centrifuging at 4 ℃ and 6000 Xg for 20 min to obtain a supernatant, wherein the protein expression SDS-PAGE map of the aminotransferase mutant supernatant is shown in figure 2. After pre-freezing the supernatant at-80 ℃, further freeze-drying the supernatant in a SCIENTZ-25T freeze dryer (Ningbo Xinzhi Biotechnology Co., ltd.) to prepare transaminase enzyme powder, and refrigerating the powder at 2-8 ℃ for later use.

Example 7: application of tetrad aminotransferase mutant in preparation of D-4,4' -biphenylalanine

The reaction system was prepared by mixing 10. 10 g g of 4,4 '-biphenylpyruvic acid, 8g of dipotassium phosphate trihydrate, 50mmol/L (pH 8.5) of potassium phosphate buffer 50 g, 3.51g of 70% isopropylamine solution, 5g of 30% Tween-20 solution and 67mg of pyridoxal coenzyme phosphate, heating to 35℃under magnetic stirring, adding 0.1g (0.01 wt) of tetratransaminase mutant enzyme powder, adjusting the reaction pH to 8.5-9.0 by using 2 mol/L NaOH solution, and stopping the reaction when the reaction was followed by HPLC central control until the reaction reached 6.5 h, wherein the residue of substrate 4,4' -biphenylpyruvic acid was 0.08% (HPLC, peak surface normalization method). The reaction system was suction filtered and the filter cake was rinsed with 50mM (pH 8.5) potassium phosphate buffer 50 mL followed by purified water 50 mL. The filter cake is then heat treated with methanol 50 mL for 1 hour at 65 ℃, and the product 9.34 g is obtained by suction filtration and drying, the yield is 93.1%, the purity related to HPLC is 99.47%, and the e.e. value is 99.82%.

Example 8: amplification application of tetrad aminotransferase mutant in preparation of D-4,4' -biphenylalanine

Adding 200.0 g of 4,4 '-diphenyl pyruvic acid, 160.1 g of dipotassium phosphate trihydrate, 0.8 kg of 50mmol/L (pH 8.5) potassium phosphate buffer solution, 50.0 g of isopropylamine and Tween-20 30.2 g,250 rpm into a 3L round bottom three-neck flask, mechanically stirring, heating the reaction system to 35 ℃, adding 2.0 g (0.01 wt) of tetratransaminase mutant enzyme powder and 1.3 g of PLP monohydrate, regulating the pH of the reaction to 8.5-9.0 by adopting 2 mol/L NaOH solution, and stopping the reaction when the substrate 4,4' -diphenyl pyruvic acid is not detected after the HPLC central control tracking reaction reaches 8.0 h. The reaction system was suction filtered and the filter cake was rinsed with 50mM (pH 8.5) potassium phosphate buffer 500 mL followed by purified water 500 mL. The filter cake was further heat treated with methanol 500. 500 mL at 65℃under reflux for 1 hour, cooled to room temperature and suction filtered, and the obtained filter cake was dried at 60℃to obtain 95.4g of the product in 95.2% yield, 99.54% purity by HPLC and 99.91% e.e. (FIG. 3).

The result shows that the conversion rate of the aminotransferase tetrad mutant shown in SEQ ID NO. 2 in a reaction system of enzyme-catalyzed 4,4 '-bipyruvate, namely 0.01 wt R60G-D72A-K196N-Q199L tetrad mutant aminotransferase, is 8 h, the e.e. value of the product reaches 99.9%, and the screened R60G-D72A-K196N-Q199L tetrad aminotransferase mutant shows extremely high stereoselectivity and high efficiency in the enzymatic preparation of D-4,4' -biphenylalanine.

Claims (10)

1. A transaminase mutant characterized in that: the aminotransferase mutant is a quadruple mutant of an amino acid sequence shown in SEQ ID NO. 1, the mutation points comprise mutation from a 60 th R to a G, mutation from a 72 th D to an A, mutation from a 196 th K to an N and mutation from a 199 th Q to an L, and the amino acid sequence of the aminotransferase mutant is shown in SEQ ID NO. 3.

2. The aminotransferase mutant as set forth in claim 4, wherein the nucleotide sequence corresponding to the aminotransferase mutant is as set forth in SEQ ID NO. 4.

3. A recombinant plasmid comprising a gene encoding the transaminase mutant of any one of claims 1 or 2.

4. The recombinant plasmid according to claim 3, the plasmid is characterized in that the plasmid is pET-28a (+), pET-28b (+), pET-28c (+), pET-5b (+), pET-15b (+), pET-24a (+), pET-24c (+), pET-24d (+), pET-25b (+), pET-27b (+), pET-28c (+), pET-29a (+), pET-29b (+), pET-29c (+), pET-30b (+), pET-30c (+), pET-30 Xa/LIC, pET-30 EK/LIC, pET-31b (+), pET-32b, pET-32 EK/LIC, pET-32 Xa/LIC, pET-37b (+), pET-39b (+), pET-40b, pET-41a (+), pET-41b, pET-42b, pET-43 c (+), pET-43 b-43, pET-43, and pET-43 c-43, and/or pET-43 pET-46 EK/LIC, pET-47b (+), pET-48b (+), pET-49b (+), pET-51b (+), pET-52b (+), pQE30, pQE31, pQE32, pQE40, pBV220, pBV221, pCold-GST, pCold-IV, pCold-GST or pTrcHisC.

5. A host cell comprising the recombinant plasmid of claim 3.

6. The host cell of claim 5, wherein the host cell is selected from the group consisting of a prokaryotic cell and a eukaryotic cell.

7. The host cell of claim 5, wherein the prokaryotic cell is an E.coli BL21 (DE 3) cell.

8. Use of a transaminase mutant according to claim 1, characterized in that it catalyzes the synthesis of D-4,4 '-diphenylalanine from 4,4' -bipyruvate.

9. The use according to claim 8, wherein the pH of the catalytic hydrolysis buffer is in the range of 7.5-9.5 and the hydrolysis temperature is in the range of 25-45 ℃.

10. The use according to claim 8, wherein the pH of the catalytic hydrolysis buffer is in the range of 9.0-9.0 and the hydrolysis temperature is in the range of 30-40 ℃.

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