CN117701521A

CN117701521A - 7 alpha-hydroxysteroid dehydrogenase mutant and encoding gene and application thereof

Info

Publication number: CN117701521A
Application number: CN202311730219.2A
Authority: CN
Inventors: 钟义华; 方灿龙; 卢柳娟; 吴伟业; 郑海婷; 丘露凤
Original assignee: Zhongshan Bailing Biotechnology Co ltd
Current assignee: Zhongshan Bailing Biotechnology Co ltd
Priority date: 2023-12-15
Filing date: 2023-12-15
Publication date: 2024-03-15

Abstract

The invention relates to the technical field of biological enzyme engineering, in particular to a 7 alpha-hydroxysteroid dehydrogenase mutant and a coding gene and application thereof. Compared with the wild 7 alpha-hydroxysteroid dehydrogenase with the amino acid sequence shown as SEQ ID NO. 2, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant provided by the invention has the advantages that any one mutation of single mutation, two-two combined mutation, three combined mutation or four combined mutation is carried out at the 98 th position, the 99 th position, the 100 th position, the 101 st position and the 148 th position of the amino acid sequence shown as SEQ ID NO. 2. The 7 alpha-hydroxysteroid dehydrogenase and coenzyme regeneration system constructed by the invention can convert the substrate intermediate 1 into the key chiral intermediate 2 under the condition of room temperature, the ee value is more than 99%, the reaction condition is mild, almost no byproducts are generated, the coenzyme circulation system is stable, the subsequent separation is simple, and the invention has wide industrialized application prospect.

Description

7 alpha-hydroxysteroid dehydrogenase mutant and encoding gene and application thereof

Technical Field

The invention relates to the technical field of biological enzyme engineering, in particular to a 7 alpha-hydroxysteroid dehydrogenase mutant and a coding gene and application thereof.

Background

Obeticholic Acid (Obeticholic Acid), known as 3α,7α -dihydroxy-6α -ethyl-5β -cholanic Acid, belongs to a farnesol X receptor agonist, and indirectly inhibits the gene expression of cytochrome 7A1 (CYP 7 A1) by activating the farnesol X receptor, so that the synthesis of cholic Acid can be inhibited, and the method is used for treating primary biliary cirrhosis and nonalcoholic fatty liver disease.

Currently, obeticholic acid is prepared by chemical synthesis techniques, for example: patent document CN106749468A discloses a preparation method of obeticholic acid, which uses hyodeoxycholic acid HDCA as a starting material to sequentially perform esterification reaction, oxidation reaction, hydroxyl protection reaction, reaction with ethyl zinc bromide or diethyl zinc reagent, dehydration reaction, oxidation reaction, reduction reaction and reaction for removing hydroxyl and carboxyl protection to obtain obeticholic acid. The method not only can solve the problem of raw materials, but also can avoid severe reaction conditions such as strong alkalinity, high temperature and the like, and greatly improves the synthesis efficiency of the obeticholic acid, thereby providing a novel preparation method which has few byproducts, simple and convenient operation, mild reaction conditions and low cost and is suitable for mass production of the obeticholic acid.

Patent document CN108191939a discloses a method for preparing obeticholic acid intermediate and obeticholic acid, the synthetic route of the intermediate is:

the obeticholic acid intermediate has good stereoselectivity in the reaction process, greatly simplifies the synthesis difficulty of the obeticholic acid and reduces the synthesis cost of the obeticholic acid. The method has the advantages of safe raw materials, low cost and effective reduction of production cost.

Patent document CN110938106a discloses a method for preparing an obeticholic acid intermediate and obeticholic acid thereof, wherein the obeticholic acid intermediate is prepared by carbonyl reduction and hydroxyl protection by taking 3A-hydroxy-6-vinyl-7-oxo-cholanic acid as a raw material, and the obtained obeticholic acid intermediate contains two benzene ring structures, has strong ultraviolet absorption, is convenient for quality research by using an ultraviolet detector, ensures that the quality of the raw material in the last step is controllable, is in a solid state at room temperature, and can be refined by using conventional purification means such as recrystallization and the like; and then the reduction of palladium carbon is further used to obtain the obeticholic acid, and the reduction of the olefinic bond is finished firstly from the aspect of the reaction process, so that the follow-up reaction is convenient, the reaction yield is high, the conversion is complete, and the refining difficulty of the final product is reduced.

However, obeticholic acid or an obeticholic acid intermediate prepared by chemical synthesis technology has high environmental protection pressure, and particularly a 7-carbonyl intermediate, as shown in formula I:

when the reduction is carried out to obtain the chiral intermediate with 7 alpha configuration, selective reduction is needed, the subsequent separation is difficult, and the yield is low. According to the search, no case report exists for preparing the obeticholic acid or the obeticholic acid intermediate by an enzyme method at present.

Disclosure of Invention

In order to solve the defects of the prior art, the invention provides a 7 alpha-hydroxysteroid dehydrogenase mutant, and a coding gene and application thereof, so as to solve the technical problems of difficult separation and low yield of the prior art adopting chemical synthesis of obeticholic acid or an obeticholic acid intermediate. According to the invention, a protein three-dimensional structure simulation and a protein directed evolution technology are adopted to artificially modify 7 alpha-hydroxysteroid dehydrogenase (7 alpha-HSDH enzyme) from Escherichia coli, and the modified mutant can obviously catalyze the reaction of the intermediate 1 to generate an intermediate 2, and the ee value is more than 99%, so that the method has a good industrial application prospect.

The invention adopts specific 7 alpha-hydroxysteroid dehydrogenase (7 alpha-Hydroxysteroid Dehydrogenase,7 alpha-HSDH) to reduce 7-carbonyl, has high stereoselectivity and avoids chiral resolution. The specific reaction is as follows:

in order to solve the technical problems, the invention provides the following technical scheme:

the amino acid sequence of the wild type 7alpha-hydroxysteroid dehydrogenase derived from Escherichia coli is shown as SEQ ID NO. 2, and the nucleotide sequence of the encoding gene is shown as SEQ ID NO. 1.

The gene sequence of 7α -hydroxysteroid dehydrogenase was amplified by polymerase chain reaction (polymerase chain reaction), and NdeI and HindIII restriction enzyme sites were added to both ends of the coding region. The amplified target gene fragment is subjected to restriction enzyme digestion by restriction enzymes NdeI and HindIII, and then is connected with a pET29a (+) vector (Novagen company) subjected to double enzyme digestion, transformed and screened, and the positive plasmid 7α -HSDH-pET29a (+) obtained through screening is transferred into BL21 (DE 3) host bacteria, so that an in vitro heterologous expression system of 7α -HSDH is constructed.

The 7 alpha-hydroxysteroid dehydrogenase mutant is constructed by a directed evolution technique. The method comprises the following steps: the mutant is obtained by utilizing error-prone PCR, DNA rearrangement, semi-rational design, three-dimensional structure simulation and other directional carrying technologies, and more specifically: the invention uses three-dimensional structure simulation technique to proceed enzyme directed evolution, uses homology modeling method to simulate the three-dimensional structure of 7 alpha-hydroxysteroid dehydrogenase, uses energy minimum principle and molecular docking technique to predict one or more possible active sites related to catalysis, then makes site-directed mutation on the active sites, and screens out mutants with obviously improved activity.

Further, the potential sites for improving the activity predicted by the three-dimensional structure simulation technology are G98, G99, G100, P101 and A148, the five sites are subjected to site-directed mutagenesis respectively, and High Pressure Liquid Chromatography (HPLC) is used for screening mutants. More specifically, the method comprises the following steps: (1) When glycine (G) at position 98 is mutated to alanine (a), the catalytic activity of the mutant is increased relative to the wild-type enzyme; (2) When glycine (G) at the position 99 is mutated into alanine (A), the activity of the mutant enzyme is improved compared with that of the wild-type enzyme; (3) When glycine (G) at position 100 is mutated to valine (V), mutant enzyme activity is increased relative to the wild-type enzyme; (4) When proline (P) at the site 101 is mutated into glycine (G), the enzyme activity of the mutant is obviously improved; (5) When alanine (A) at position 148 was mutated to valine (V), the mutant enzyme activity was significantly improved. When the above-mentioned 5-site mutations are subjected to two-by-two or three or four combination mutations, the catalytic activity of the mutant is greatly improved as compared with the single mutant.

Therefore, the invention provides a 7 alpha-hydroxysteroid dehydrogenase mutant, which has an amino acid sequence which is subjected to any one mutation of single mutation, two-two combined mutation, three combined mutation or four combined mutation at the 98 th, 99 th, 100 th, 101 th and 148 th positions of the amino acid sequence shown in SEQ ID NO. 2 compared with the wild type 7 alpha-hydroxysteroid dehydrogenase with the amino acid sequence shown in SEQ ID NO. 2.

Further, the single mutation of the 7α -hydroxysteroid dehydrogenase mutant is:

when the 98 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 4;

or when the 99 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 6;

or when the 100 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 8;

or when the 101 st position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from proline to glycine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 10;

or when the 148 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from alanine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 12.

Further, the combination mutation of the 7 alpha-hydroxysteroid dehydrogenase mutant is as follows:

when the 98 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the 100 th position is mutated from glycine to valine, and the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 14.

Further, the three combined mutations of the 7α -hydroxysteroid dehydrogenase mutants are:

when the 100 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to valine, the 101 st position is mutated from proline to glycine, the 148 th position is mutated from alanine to valine, and the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 16.

Further, the four combined mutations of the 7α -hydroxysteroid dehydrogenase mutants are:

when the 99 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the 100 th position is mutated from glycine to valine, the 101 th position is mutated from proline to glycine, the 148 th position is mutated from alanine to valine, and the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 18.

In addition, the invention also provides a coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant.

Specifically, the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 4 is shown as SEQ ID NO. 3;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 6 is shown as SEQ ID NO. 5;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 8 is shown as SEQ ID NO. 7;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 10 is shown as SEQ ID NO. 9;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 12 is shown as SEQ ID NO. 11;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 14 is shown as SEQ ID NO. 13;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 16 is shown as SEQ ID NO. 15;

or the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown as SEQ ID NO. 18 is shown as SEQ ID NO. 17.

According to the prior public knowledge, any gene is connected into various expression vectors after being operated or transformed, is transformed into a proper host cell, and can over-express target protein through induction under proper conditions.

Furthermore, the invention also claims a vector containing the coding gene.

Specifically, the vector may be any of various expression vectors including, but not limited to, pET expression vector, pCW expression vector, pUC expression vector, or pPIC9k expression vector.

Furthermore, the invention also claims host cells containing the coding genes.

In particular, the host cell may be any suitable host cell including, but not limited to, E.coli, pichia pastoris, streptomyces, or Bacillus subtilis.

In addition, the invention also provides application of the 7 alpha-hydroxysteroid dehydrogenase mutant, the coding gene, the vector and the host cell in preparation of the obeticholic acid chiral intermediate-2, which is specifically as follows: the 7 alpha-HSDH enzyme mutant, the coding gene, the vector and the host cell are used as biocatalysts to transform substrates (the intermediate 1) to generate products (the intermediate 2).

Further, the invention also provides a method for preparing the obeticholic acid chiral intermediate-2, which comprises the following steps of:

s1, configuring a reaction system, which comprises the following steps: 1-10 g/L of 7 alpha-hydroxysteroid dehydrogenase mutant, 50-200 mmol/L of sodium phosphate buffer solution with pH of 6.0-8.0, 0.1-0.5 g/L of coenzyme NADP+, 40-60 g/L of obeticholic acid chiral intermediate-1, 25-40 g/L of glucose, 1g/L of glucose dehydrogenase, and regulating the pH of a reaction system to 6.0-8.0; controlling the temperature of the reaction system to be 30 ℃ and stirring for reaction;

s2, performing HPLC detection after reacting for 24 hours to obtain the obeticholic acid chiral intermediate-2. After the reaction, the product is verified by HPLC, and the reaction conversion rate is more than 60%.

The enzyme for performing biocatalytic reaction in the method for preparing the obeticholic acid chiral intermediate-2 provided by the invention comprises pure enzyme, corresponding recombinant resting cells, crude enzyme liquid or crude enzyme powder and other existing forms.

In summary, compared with the prior art, the invention has the following beneficial effects:

the 7 alpha-hydroxysteroid dehydrogenase and coenzyme regeneration system constructed by the invention can convert the substrate intermediate 1 into the key chiral intermediate 2 under the condition of room temperature, the ee value is more than 99%, the reaction condition is mild, almost no byproducts are generated, the coenzyme circulation system is stable, the subsequent separation is simple, and the invention has wide industrialized application prospect.

Detailed Description

The present invention will be described in further detail with reference to the following examples, which are not intended to limit the present invention, but are merely illustrative of the present invention. The experimental methods used in the following examples are not specifically described, but the experimental methods in which specific conditions are not specified in the examples are generally carried out under conventional conditions, and the materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

In the examples, the experimental procedures, which are not specified in particular conditions, are generally carried out according to conventional conditions, such as those described in the guidelines for molecular cloning experiments (J. Sambrook, D.W. Lassel, huang Peitang, wang Jiaxi, zhu Houchu, et cetera, third edition, beijing: science Press, 2002).

Example 1 construction of prokaryotic expression System

The 7α -HSDH gene fragment was amplified by polymerase chain reaction using the genomic DNA of E.coli BL21 (DE 3) as a template, and a specific forward primer (5'CGGGAATTCCATATGTTTAATTCTGACAACCTG 3') (SEQ ID NO: 19) and a reverse primer (5'CCCAAGCTTAATTGAGCTCCTGTACC 3') (SEQ ID NO: 20). The amplified target fragment was separated by 1% agarose gel electrophoresis and subjected to gel cutting recovery (gel recovery kit was purchased from Tiangen Biochemical technologies (Beijing) Co., ltd.).

The target fragment was recovered, digested with restriction enzymes NdeI and HindIII (available from New England Biolabs, NEB) at 37℃for 20 hours, and separated by 1% agarose gel electrophoresis and digested. Followed by ligation overnight at 16℃with the expression vector pET29a (+) (Novagen) subjected to the same double cleavage under the action of T4 DNA ligase (available from Takara). The ligation solution transformed DH 5. Alpha. Competent cells (purchased from Tiangen Biochemical technology (Beijing)) and subjected to colony PCR screening and sequencing verification to obtain the positive recombinant plasmid 77. Alpha. -HSDH-pET29a (+).

The positive recombinant plasmid 7alpha-HSDH-pET 29a (+) is transformed into expression host bacterium BL21 (DE 3) (purchased from Tiangen Biochemical technology (Beijing) limited company) to obtain prokaryotic expression strain 7alpha-HSDH-pET 29a (+)/BL 21 (DE 3) which is used as a primary strain for subsequent directed evolution and fermentation.

Example 2 shake flask fermentative preparation of enzymes

The expression strain 7α -HSDH-pET29a (+)/BL 21 (DE 3) constructed in example 1 was cultured overnight at 37℃with shaking in 5mL of LB liquid medium [10g/L tryptone (OXIO), 5g/L yeast powder (OXIO), 10g/L sodium chloride (Guog reagent) ] added with kanamycin sulfate at a final concentration of 30. Mu.g/mL, and then inoculated in 500mL of LB liquid medium containing kanamycin sulfate at a final concentration of 30. Mu.g/mL at a ratio of 1% (V/V) with shaking at 200rpm at 37 ℃. When the OD600 is between 0.8 and 1.0, the inducer IPTG (isopropyl-. Beta. -D-thiogalactoside, IPTG) is added at a final concentration of 0.1mmol/L and induced overnight at 30 ℃. The thalli are collected by centrifugation at the temperature of 4 ℃ and at the speed of 8000rpm, then suspended in 50mmol/L sodium phosphate buffer solution with pH of 7.0, and are subjected to ultrasonic crushing (200W, 3s/5s,20 min), centrifugation at the temperature of 4 ℃ and at the speed of 12000rpm for 20min, and the supernatant is taken for freeze drying, thus obtaining crude enzyme powder.

Example 3 construction and screening of mutants

1. Construction of the mutant:

the three-dimensional structure simulation of the 7alpha-HSDH is carried out by adopting a homologous modeling method, and the five possible mutation sites and mutation amino acids are predicted by utilizing the molecular docking and energy minimum principle, and are preliminarily determined as five sites of G98A, G99A, G100V, P101G, A V. Then site-directed mutagenesis was performed on each of these sites using the 7α -HSDH-pET29a (+) recombinant plasmid as a template (for specific mutagenesis operations, reference is made to Stratagene Corp.)Site-Directed Mutagenesis Kit description of operation). Wherein:

(1) 98 site mutation

Forward primer (SEQ ID NO: 21):

TTCTGGTTAACAACGCCGGTGCCGGTGGACCTAAACCGTTTGA，

reverse primer (SEQ ID NO: 22):

TCAAACGGTTTAGGTCCACCGGCACCGGCGTTGTTAACCAGAA；

(2) 99 site mutation

Forward primer (SEQ ID NO: 23):

TGGTTAACAACGCCGGTGGCGCTGGACCTAAACCGTTTGATAT，

reverse primer (SEQ ID NO: 24):

ATATCAAACGGTTTAGGTCCAGACGCCACCGGCGTTGTTAACCA，

(3) 100 site mutation

Forward primer (SEQ ID NO: 25):

TTAACAACGCCGGTGGCGGTGTACCTAAACCGTTTGATATGCC，

reverse primer (SEQ ID NO: 26):

GGCATATCAAACGGTTTAGGTACACCGCCACCGGCGTTGTTAA；

(4) 101 site mutation

Forward primer (SEQ ID NO: 27):

ACAACGCCGGTGGCGGTGGAGGTAAACCGTTTGATATGCCAAT，

reverse primer (SEQ ID NO: 28):

ATTGGCATATCAAACGGTTTACCTCCACCGCCACCGGCGTTGT；

(5) 148 site mutation

Forward primer (SEQ ID NO: 29):

TTCTGACCATCACTTCTATGGTGGCAGAAAATAAAAATATAAAC，

reverse primer (SEQ ID NO: 30):

GTTTATATTTTTATTTTCTGCCACCATAGAAGTGATGGTCAGAA。

2. mutant culture:

after transforming BL21 (DE 3) host bacteria with the above-obtained plasmid, the plasmid was spread on LB solid medium containing 30. Mu.g/mL kanamycin, and cultured upside down at 37℃overnight, followed by picking up the monoclonal culture from the plate overnight. The overnight cultured bacterial liquid was transferred to an Erlenmeyer flask containing fresh LB medium, and after shaking culture at 37℃and 200rpm for 4 hours, IPTG was added to the resulting culture to give a final concentration of 0.1mmol/L for induction, and the resulting culture was incubated overnight at 30 ℃. The cells were collected by centrifugation at 4000rpm for 10min at 4℃and suspended in 50mmol/L sodium phosphate buffer pH7.0, followed by ultrasonication and screening.

3. Screening of mutants:

10g/L substrate concentration, 0.2g/L NADP+,10g/L glucose, 50mmol/L sodium phosphate buffer pH7.0, 1g/L glucose dehydrogenase (self-made), 10% of the prepared cell disruption solution was added, and the mixture was subjected to shaking reaction at 30℃and 220 rpm. Samples were taken at 2h and 24h, respectively, for HPLC detection and the unit enzyme activity for substrate intermediate 1 was calculated.

Clones with significantly improved substrate conversion rates at both 2h and 24h were subjected to extensive culture and then sequenced to verify mutation status. Sequencing results show that the mutant enzyme activity is significantly improved, and the mutation sites contained in the clone are as follows: glycine (G) at position 98 was mutated to alanine (a), glycine (G) at position 99 was mutated to alanine (a), glycine (G) at position 100 was mutated to valine (V), proline (P) at position 101 was mutated to glycine (G), and alanine (a) at position 148 was mutated to valine (V).

And then carrying out pairwise combined mutation, three combined mutations and four combined mutations on the 5 sites, wherein the activity detection shows that the catalytic activity of the combined mutations of certain sites is obviously improved compared with that of single-point mutations, and the specific enzyme activity values are shown in the following table 1.

Table 1 enzyme Activity of different combinations of mutations

1U relative to the amount of enzyme required to produce 1. Mu. Mol of product in 1 min.

Wherein:

when the 98 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 4, and correspondingly, the nucleotide sequence of the encoding gene is shown in SEQ ID NO. 3.

When the 99 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 6, and correspondingly, the nucleotide sequence of the encoding gene is shown in SEQ ID NO. 5.

When the 100 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 8, and correspondingly, the nucleotide sequence of the encoding gene is shown in SEQ ID NO. 7.

When the 101 st position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from proline to glycine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 10, and correspondingly, the nucleotide sequence of the encoding gene is shown in SEQ ID NO. 9.

When the 148 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from alanine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 12, and correspondingly, the nucleotide sequence of the encoding gene is shown in SEQ ID NO. 11.

When the 98 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the 100 th position is mutated from glycine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 14, and correspondingly, the nucleotide sequence of the encoding gene is shown in SEQ ID NO. 13.

When the 100 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to valine, the 101 st position is mutated from proline to glycine, the 148 th position is mutated from alanine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown in SEQ ID NO. 16, and correspondingly, the nucleotide sequence of the coding gene is shown in SEQ ID NO. 15.

When the 99 th position of the amino acid sequence shown in SEQ ID NO. 2 is mutated from glycine to alanine, the 100 th position is mutated from glycine to valine, the 101 th position is mutated from proline to glycine, the 148 th position is mutated from alanine to valine, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is shown as SEQ ID NO. 18, and correspondingly, the nucleotide sequence of the encoding gene is shown as SEQ ID NO. 17.

The specific sequence is as follows:

(1) Wild type 7α -hydroxysteroid dehydrogenase encoding gene nucleotide sequence (SEQ ID NO: 1):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGGTGGACCTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGCGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(2) Wild-type 7α -hydroxysteroid dehydrogenase amino acid sequence (SEQ ID NO: 2):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGGGPKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMAAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(3) The nucleotide sequence of the G98A mutant encoding gene (SEQ ID NO: 3):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGCCGGTGGACCTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGCGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(4) The amino acid sequence of the G98A mutant (SEQ ID NO: 4):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGAGGPKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMAAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(5) The nucleotide sequence of the G99A mutant encoding gene (SEQ ID NO: 5):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGCTGGACCTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGCGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(6) The amino acid sequence of the G99A mutant (SEQ ID NO: 6):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGAGPKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMAAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(7) G100V mutant encoding gene nucleotide sequence (SEQ ID NO: 7):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGGTGTACCTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGCGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(8) G100V mutant amino acid sequence (SEQ ID NO: 8):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGGVPKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMAAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(9) The nucleotide sequence of the P101G mutant encoding gene (SEQ ID NO: 9):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGGTGGAGGTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGCGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(10) P101G mutant amino acid sequence (SEQ ID NO: 10):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGGGGKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMAAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(11) A148V mutant encoding gene nucleotide sequence (SEQ ID NO: 11):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGGTGGACCTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGTGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(12) A148V mutant amino acid sequence (SEQ ID NO: 12):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGGGPKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMVAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(13) The nucleotide sequence of the G98A/G100V mutant encoding gene (SEQ ID NO: 13):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGCCGGTGTACCTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGCGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(14) The amino acid sequence of the G98A/G100V mutant (SEQ ID NO: 14):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGAGVPKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMAAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(15) G100V/P101G/A148V mutant encoding gene nucleotide sequence (SEQ ID NO: 15):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGGTGTAGGTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGTGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(16) G100V/P101G/A148V mutant amino acid sequence (SEQ ID NO: 16):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGGVGKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMVAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

(17) The nucleotide sequence of the G99A/G100V/P101G/A148V mutant encoding gene (SEQ ID NO: 17):

ATGTTTAATTCTGACAACCTGAGACTCGACGGAAAATGCGCCATCATCACAGGTGCGGGTGCAGGTATTGGTAAAGAAATCGCCATTACATTCGCGACAGCTGGCGCATCTGTGGTGGTCAGTGATATTAACGCCGACGCAGCTAACCATGTTGTAGACGAAATTCAACAACTGGGTGGTCAGGCATTTGCCTGCCGTTGTGATATTACTTCCGAACAGGAACTCTCTGCACTGGCAGACTTTGCTATCAGTAAGCTGGGTAAAGTTGATATTCTGGTTAACAACGCCGGTGGCGCTGTAGGTAAACCGTTTGATATGCCAATGGCGGATTTTCGCCGTGCTTATGAACTGAATGTGTTTTCTTTTTTCCATCTGTCACAACTTGTTGCGCCAGAAATGGAAAAAAATGGCGGTGGCGTTATTCTGACCATCACTTCTATGGTGGCAGAAAATAAAAATATAAACATGACTTCCTATGCATCATCTAAAGCTGCGGCCAGTCATCTGGTCAGAAATATGGCGTTTGACCTAGGTGAAAAAAATATTCGGGTAAATGGCATTGCGCCGGGGGCAATATTAACCGATGCCCTGAAATCCGTTATTACACCAGAAATTGAACAAAAAATGTTACAGCACACGCCGATCAGACGTCTGGGCCAACCGCAAGATATTGCTAACGCAGCGCTGTTCCTTTGCTCGCCTGCTGCGAGCTGGGTAAGCGGACAAATTCTCACCGTCTCCGGTGGTGGGGTACAGGAGCTCAATTAA

(18) G99A/G100V/P101G/A148V mutant amino acid sequence (SEQ ID NO: 18):

MFNSDNLRLDGKCAIITGAGAGIGKEIAITFATAGASVVVSDINADAANHVVDEIQQLGGQAFACRCDITSEQELSALADFAISKLGKVDILVNNAGGAVGKPFDMPMADFRRAYELNVFSFFHLSQLVAPEMEKNGGGVILTITSMVAENKNINMTSYASSKAAASHLVRNMAFDLGEKNIRVNGIAPGAILTDALKSVITPEIEQKMLQHTPIRRLGQPQDIANAALFLCSPAASWVSGQILTVSGGGVQELN

example 4 biocatalysis of mutants

4g of the substrate (intermediate 1) was dissolved in 100mL of 50mmol/L sodium phosphate buffer pH9.0, and the pH was adjusted to 7.0 with a liquid base, and after the substrate was completely dissolved, 2.5g of glucose, 0.02g of NADP+, 1g of 7. Alpha. -HSDH mutant lyophilized powder (7. Alpha. -HSDH mutant lyophilized powder prepared in example 2) and 0.1g of glucose dehydrogenase lyophilized powder were added. The reaction solution was placed in a water bath at a constant temperature of 30℃and was stirred mechanically to control the pH of the system to 7.0 using a 2mol/L sodium hydroxide solution, and after 24 hours of reaction, HPLC detection was performed and the substrate conversion was as shown in Table 2.

TABLE 2 conversion of mutants

Finally, it should be noted that the above description is only for illustrating the technical solution of the present invention, and not for limiting the scope of the present invention, and that the simple modification and equivalent substitution of the technical solution of the present invention can be made by those skilled in the art without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A7 alpha-hydroxysteroid dehydrogenase mutant is characterized in that compared with a wild-type 7 alpha-hydroxysteroid dehydrogenase with an amino acid sequence shown as SEQ ID NO. 2, the amino acid sequence of the 7 alpha-hydroxysteroid dehydrogenase mutant is subjected to any one mutation of single mutation, two-by-two combined mutation, three combined mutation or four combined mutation at the 98 th, 99 th, 100 th, 101 th and 148 th positions of the amino acid sequence shown as SEQ ID NO. 2.

2. The 7α -hydroxysteroid dehydrogenase mutant of claim 1, wherein the single mutation is:

3. The 7α -hydroxysteroid dehydrogenase mutant of claim 1, wherein the pairwise combination of mutations are:

4. The 7α -hydroxysteroid dehydrogenase mutant of claim 1, wherein the three combined mutations are:

5. The 7α -hydroxysteroid dehydrogenase mutant of claim 1, wherein the four combined mutations are:

6. The coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant according to any one of claims 2 to 5, wherein the nucleotide sequence of the coding gene of the 7 alpha-hydroxysteroid dehydrogenase mutant with the amino acid sequence shown in SEQ ID NO. 4 is shown in SEQ ID NO. 3;

7. A vector comprising the coding gene of claim 6, wherein the vector is a pET expression vector, a pCW expression vector, a pUC expression vector or a pPIC9k expression vector.

8. A host cell comprising the coding gene of claim 6, wherein the host cell is escherichia coli, pichia pastoris, streptomyces, or bacillus subtilis.

9. Use of a 7α -hydroxysteroid dehydrogenase mutant according to any one of claims 1 to 5, a coding gene according to claim 6, a vector according to claim 7, a host cell according to claim 8 for the preparation of obeticholic acid chiral intermediate-2.

10. A process for the preparation of obeticholic acid chiral intermediate-2 comprising the steps of:

s1, configuring a reaction system, which comprises the following steps: 1-10 g/L of 7 alpha-hydroxysteroid dehydrogenase mutant according to any one of claims 1-5, 50-200 mmol/L of sodium phosphate buffer solution with pH of 6.0-8.0, 0.1-0.5 g/L of coenzyme NADP+, 40-60 g/L of obeticholic acid chiral intermediate-1, 25-40 g/L of glucose, 1g/L of glucose dehydrogenase, and adjusting the pH of the reaction system to 6.0-8.0; controlling the temperature of the reaction system to be 30 ℃ and stirring for reaction;

s2, performing HPLC detection after reacting for 24 hours to obtain the obeticholic acid chiral intermediate-2.