KR100330359B1 - Novel esterase derived from Pseudomonas aeruginosa, its gene and process for production of optically active carboxylic acids using them - Google Patents

Abstract

The present invention relates to a novel Pseudomonas aeruginosa isolated from soil, a novel esterase derived therefrom, and a method for producing an optically active carboxylic acid using the same, more specifically from the above strains. A novel esterase and its gene, which are isolated and can produce an optically active carboxylic acid represented by Formula 1 from carboxylic ester racemates, and recombinant expression vectors and transformants obtained by cloning the esterase genes; And a method for producing an optically active carboxylic acid using the same. Using the esterases of the present invention, optically active carboxylic acids useful in the production of physiologically active pharmaceuticals, in particular captopril and analapril, which are therapeutic agents for hypertension, can be obtained by a simple method of high yield.

(Wherein R ₁ , R ₂ and n are as defined in the specification).

Description

Novel esterase derived from Pseudomonas aeruginosa, its gene and process for production of optically active carboxylic acids using them}

The present invention is Pseudomonas irruzinosa, a microorganism which selectively produces an optically active carboxylic acid of Formula 1 and its enantiomeric ester thereof by asymmetrically hydrolyzing a carboxylic ester racemate and a novel ester derived therefrom. And a method for producing an optically active carboxylic acid using the same.

More specifically, the present invention is a novel esterase derived from Pseudomonas irruginosa; The esterase gene; A recombinant expression vector comprising the gene; Transformants transformed with the expression vector; It relates to a method of culturing the transformant to obtain an optically active carboxylic acid from the culture.

Formula 1

Wherein R ₁ is alkyl, aralkyl or aryl, R ₂ is alkyl and n is 1 or 2.

Optically active carboxylic acids can be used in various bioactive drugs, in particular captopril (Ondettii et al ., Science 196 , 441 (1977)) and analapril (Japanese Patent Publication No. 18599) is used as a useful raw material for the production. According to the FDA's Policy Statement for the Development of New Stereoisomeric Drug in 1992, the FDA issued a new chiral drug to obtain FDA approval. It is recommended that it be a single stereoisomer in an optical three-dimensional form. However, when the pharmaceutical product is produced in racemic form, it is required to prove that it is safe for animals and humans not only when used in the racemic form but also when each isomer is used separately. It has the effect of regulating the production of pharmaceutical intermediates indirectly but almost in principle. This is because, in most cases, the biological activity of a drug, which is an optical isomer, is represented by one stereoisomer, and the other is rather side effect or toxic. Therefore, research on the production of chiral compounds useful for the production of optically active pharmaceuticals has emerged as an indispensable research project in order to secure the competitiveness of the pharmaceutical industry and promote public health.

Among the optical isomers, ACE-based inhibitors (Angiotensin-Converting Enzyme inhibitors), enalapril and captopril, occupy the most important position in the global pharmaceutical market with about 30% of the market size, and their major intermediates (R)- Development of biological production technology of 2-hydroxy-4-phenyltanoate and (R) -β-acetylmercaptoisobutyrate is urgent.

Since the cost of production of optically active pharmaceutical products depends on the production cost of intermediates and their characteristics, the import of optically active intermediates can be compared with the import of finished products, and their production technology is also high value added, which avoids the transfer of technology. In some cases, the export of the optically active intermediate itself may be avoided, and the introduction of this technology is almost hopeless. Therefore, it may be best to obtain optically active intermediates as close to the final product as possible, and from this point of view the development of biological production processes for the useful optically active intermediates (R) -β-acetylmercaptoisobutyrate is a major optically active drug. It can be used as a precursor useful for the production of phosphorus captopril, tocopherol, lasaloside A, calciycin, lactam antibiotics, (R)-and (S) -muscone and the like.

The optically active carboxylic acid may be produced by asymmetric hydrolysis using esterases from carboxylic acid racemates represented by the formula (2).

R ₁ , R ₂ and n in the above formula are as defined in Formula 1, and R ₃ is alkyl.

In general, the method of producing optically active carboxylic acid by chemical synthesis has encountered many difficulties due to low reaction selectivity, complex optical splitting method and serious environmental pollution, and has been decisive factor in economic efficiency. Therefore, as an alternative to this, a method for producing an optically active agent using a biocatalyst such as a microorganism or an enzyme has recently been developed.

Among microorganisms, strains having activity of selectively hydrolyzing only (R)-or (S) -carboxylic acid esters have been reported (Japanese Patent Laid-Open No. 1-222798). . However, the esterases produced by the microorganisms in this patent are in small amounts, and are not suitable for mass production of optically active carboxylic acids using them. Therefore, research is focused on a technique for cloning an esterase gene isolated from a microorganism and expressing it in E. coli using a general gene recombination technique.

In one such study, esterases derived from Pseudomonas fluorescens IFO3018, which act specifically on (R) -esters from carboxylic ester racemates to produce optically active (R) -carboxylic acids Since the gene was isolated, its nucleotide sequence and amino acid sequence were disclosed, and a technique for producing a recombinant esterase by transgenic E. coli containing the gene has been reported (Japanese Patent Laid-Open Publication No. 64-67190), Pseudomonas puti The Pseudomonas putida FERM BP-3846-derived esterase gene was also cloned to reveal the nucleotide sequence and the amino acid sequence estimated therefrom. Similarly, the expression technique by transformed Escherichia coli and the physical properties of the recombinant esterase produced therefrom This has been reported (US Pat. No. 5308765, US Pat. 5542847, Ozaki et al., Biosci. Biotech. Biochem . 59 , 1204 (1992)).

The base sequence and amino acid sequence of esterases derived from these two microorganisms differed from each other.Esterases derived from Pseudomonas fluorescens consisted of 218 amino acids and esterases derived from Pseudomonas putida consisted of 276 amino acids do. The heat stability of the two enzymes was 70 ° C. for Pseudomonas putida derived esterase, higher than 50 ° C. for Pseudomonas fluorescens derived esterase. The molecular weight of Pseudomonas putida derived esterase was about 30,000 Daltons with an isoelectric point of pH 3.90 ± 0.1, optimum pH 7.0 and stable at pH 6.0-8.0.

The present inventors have studied to find new strains producing optically active carboxylic acids and novel esterases derived therefrom, and showed stability even above 70 ° C from Pseudomonas aeruginosa isolated from soil (R The present invention was completed by separating a novel esterase of about 35 kDa that selectively produces) -carboxylic acid and the gene encoding it.

It is an object of the present invention to provide a novel esterase enzyme protein which is stable even at high temperatures and specifically acts on carboxylic ester racemates to produce optically active carboxylic acids and genes encoding them.

It is also an object of the present invention to provide a novel strain producing the esterase and to reveal its physicochemical properties.

In addition, an object of the present invention is to provide a method for transforming E. coli strains using a recombinant expression vector cloned with the esterase gene, and culturing the transformed strain to produce an esterase enzyme from the culture. .

Finally, an object of the present invention is to provide a method for producing an optically active carboxylic acid using the esterase enzyme.

1 is a schematic diagram showing a cloning process of a gene encoding an esterase producing (R) -carboxylic acid,

Figure 2 shows the restriction map and location analysis of the gene encoding the esterase to produce (R) -carboxylic acid,

B: Bam H I, H: Nhe I, N: Nco I, R: Nru I, K: Kpn I, B1: Bam H I / Sau 3A

RAM: (R) -acetylmercaptoisobutyrate

(pTBL7, pTBL71, pTBL72 are inserted into the pBluescript (R) KSII + vector, the other inserts are inserted into the pUC119 cloning vector, and '+' and '-' indicate RAM production.)

3A and 3B show a result of comparing the homology of the amino acid sequence of the esterase producing (R) -carboxylic acid with other esterases,

1 : Esterase gene est A

2 : triacylglycerol lipase ( Moraxella sp.)

3, 4 : triacylglycerol lipase ( Psychrobacter immobilis )

5, 6 : carboxyl esterase ( Acinetobacter calcoaceticus )

4 is a restriction map showing the structure of the recombinant esterase expression vector pES22b,

Ap : ampicillin resistance gene

lac I : β-galactosidase gene

Figure 5 shows the results of SDS-PAGE analysis of proteins containing an esterase expressed from pES22b by culturing recombinant E. coli PES,

1 : 4 hours, 2 : 2 hours, 3 : 1 hour, 4 : 0 hours, M : protein marker

FIG. 6 is a gas chromatogram of a diastereomer synthesized from standard (R) and (S) acetylmercaptoisobutyrate and acetylmercaptoisobutyrate produced by recombinant esterase.

(a) : Diastereomer of acetylmercaptoisobutyrate produced by recombinant E. coli BL21 PES

(b) : Standard (S) -acetylmercaptoisobutyrate (ii) and (R) -acetylmercaptoisobutyrate (iii)

In order to achieve the above object, the present invention provides a novel esterase enzyme protein derived from Pseudomonas genus strain. The esterase enzyme has an amino acid sequence set forth in SEQ ID NO: 2, has a molecular weight of 35,000 Daltons, and an isoelectric point is pH 6.4.

The esterase is isolated from Pseudomonas aeruginosa and selectively produces optically active (R)-or (S) -carboxylic acid esters by asymmetric hydrolysis of carboxylic ester racemates. Have activity.

The amino acid sequence of the esterase of the present invention was derived from the genus Moraxella sp., Psychrobacter immobilis , triacylglycerol lipase and acinetobacter calcoaceticus. Consensus of glycine-X-serine-X-glycine (GXSXG) containing serine, which is the 169th amino acid of the esterase isolated in the present invention, as compared with the amino acid sequence of the carboxyl esterase derived from sequences) were in common. The serine residue is known as an active central site of an enzyme such as an esterase. In the esterase of the present invention, another common sequence of histidine-glycine (His-Gly), which assists in the activity of the common sequence, is weak in the serine residue. Located in front of 70 amino acids, it is characteristic of typical serine esterases.

The present invention also provides a gene encoding the esterase. The gene has a nucleotide sequence set forth in SEQ ID NO: 1 and has a CDS (coding sequence) set forth in SEQ ID NO: 3. The G + C ratio of the entire base sequence is 67.41%. The inventors have registered the gene sequence of the esterase in the US GenBank accession number AF170828.

In another aspect, the present invention provides a Pseudomonas aeruginosa Pseudomonas strain Pseudomonas producing the esterase. Specifically, strains were selected from primary samples containing (R, S) -acetylmercaptoisobutylic acid methyl ester and pH indicators from soil samples collected from all over Korea and India. By culturing, the carboxylic acid bioconversion strain was selected through color change of the culture. The first selected strains were analyzed by gas chromatography (GC) to finally select strains having excellent (R) -carboxylic acid production capacity.

As a result of measuring and determining the fatty acid and quinone composition and content of the isolated optically active carboxylic acid producing strains, C _{18: 1} and C _{16: 0} were present as the main constituents of the fatty acid. 3-OH C _{10: 0} , 3-OH C _{12: 0} were characteristically present. In addition, quinone, which is an important chemical taxonomy of microorganisms, contained ubiquinone-9. In summary, the strains of the present invention were identified as Pseudomonas genus, and 16S ribosomal RNA sequences were identified as Pseudomonas irruginosa as homology of 99.9% for species determination. It became. The strain was deposited by the inventors of the Biotechnology Research Institute Gene Bank on August 4, 1999 (Accession No .: KCTC 8953P).

On the other hand, in order to produce a large amount of the esterase obtained in the above was prepared a recombinant esterase expression vector. First, two oligonucleotides having the nucleotide sequences shown in SEQ ID NO: 4 and SEQ ID NO: 5 were synthesized to facilitate purification of the esterase. DNA fragments designed to encode six histidines at the C-terminus of the estA gene were amplified by performing the polymerase chain reaction using the oligonucleotides as the est A gene N-terminal primers and the C-terminal primers, respectively. The extracted DNA fragment was inserted into a blunt cleavage site of the restriction enzyme Eco R I of pT7blue vector, which is a PCR cloning vector, to prepare a pT7ES vector, and then partially cleave the pT7ES and pET22b with Nco I. Recombinant esterase expression vector pES22b was prepared by ligation (see FIG. 1 ). The restriction map of the expression vector pES22b prepared as above is shown in FIG. 4 . The pES22b was transformed into Escherichia coli BL21 to obtain a recombinant Escherichia coli strain BL21 PES, which was deposited on August 4, 1999 to the Biotechnology Research Institute Gene Bank (Accession Number: KCTC8952P).

The recombinant E. coli strains were cultured to recover the cells, and then disrupted to isolate the recombinant esterase from the supernatant. In order to investigate the activity of the recombinant esterase, (R, S) -acetylmercaptoisobutyl acid methyl ester was hydrolyzed to a substrate, and compared to the GC analysis of the chemically synthesized diastereomer, the esterase of the present invention. The optical activity of the acetylmercaptoisobutyrate produced by the agent was investigated. As a result, it was found that the optically active carboxylic acid produced by the recombinant esterase of the present invention was (R) type. In general, when (R) -acetylmercaptoisobutyrate is produced from (R, S) -acetylmercaptoisobutyl acid methyl ester by a chemical method, the (S) form is produced in the form of a mixed racemate. On the other hand, in the case of using the esterase of the present invention, since the carboxylic acid having only the optical activity of the (R) type is easily separated, it can be used to prepare the optically active carboxylic acid used in the manufacture of various medicines.

Meanwhile, in order to investigate the thermal stability of the recombinant esterase produced by the recombinant E. coli of the present invention, the cultured cells were crushed and centrifuged to maintain the supernatant containing the esterase at different temperatures, and then, at 30 ° C. The activity was investigated. As a result, the activity of the recombinant esterase of the present invention was hardly changed even at 70 ° C. From this, it can be seen that the esterase of the present invention has thermal stability even at a high temperature of 70 ° C or higher.

Hereinafter, the present invention will be described in detail by way of examples.

However, the following examples are illustrative of the present invention, and the content of the present invention is not limited thereto.

Example 1 Isolation of Esterase Producing Strains with Asymmetric Hydrolytic Activity

Strains were selected from the samples collected from domestic and Indian soils. First, 1 g soil sample was suspended in 9 ml of distilled water, and the solution was diluted 10 times, 100 times, and 1000 times. The soil suspension was plated in 200 μl each in a nutrient medium (bacto beef extract 3g / l, peptone 5g / l, agar 15g / l) and incubated in a 30 ° C. incubator for 24 hours. The strains grown here were purely separated, and among them, optically active carboxylic acid producing strains were isolated using a primary selection liquid medium. The composition of the primary selection medium was (R, S) -acetylmercaptoisobutyric acid methyl ester (v), 1 v / v%, bromocresol purple, pH indicator 0.1 w / v%, 0.05M potassium phosphate buffer (potassium phosphate buffer, pH 7.0).

Pure strains were inoculated in 1 ml of primary selection medium and incubated in a 30 ° C. incubator for 3 hours, and then the color change of the culture was investigated. Since bromocresol purple has a violet color at pH 6.8 and yellow at pH 3.2, the strain producing optically active carboxylic acid from the carboxylic acid ester has a lower pH when the culture medium is yellow. Therefore, only strains that turned yellow in culture were selected as carboxylic acid bioconversion strains. The primary selected samples were analyzed by gas chromatography (HEWLEET PACKARD 5890) to select strains with excellent final (R) -carboxylic acid production capacity.

As described above, in order to select the strain having the highest production ability of (R) -carboxylic acid among the 21 selected strains, glucose medium (glucose 2.66%, ammonium sulfate 0.5%, yeast extract 0.066%, corn steep liquor 2.0%, liquid culture was carried out using (pH 6.8-7.0). After incubation with stirring at 150 ° C. at 30 ° C. for 24 hours, the cells obtained by centrifugation at 3000 rpm for 30 minutes were used in a bioconversion experiment. Strain No. 1 showing the highest yield of (R) -carboxylic acid among the 21 selected strains. 1001 was selected as a good strain.

Example 2 Identification of Isolated Strains

(R) -carboxylic acid bioconversion strain No. 1 selected in Example 1. The identification of 1001 was made by measuring the composition and content of fatty acids and quinones and comparing them with existing databases, and the determination and analysis were carried out by Yoon et al., Int. J. Syst. Bacteriol. , 47 , 933. , 1997).

As a result of fatty acid analysis, C _{18: 1} and C _{16: 0} were present as the main components of fatty acids, and 3-OH C _{10: 0} and 3-OH C _{12: 0} were characteristically represented as hydroxyl fatty acids. In addition, quinone, which is an important chemical taxonomy of microorganisms, contained ubiquinone-9. In summary, the strain of the present invention was identified as Pseudomonas sp. Meanwhile, 16S ribosomal DNA sequences were examined for species determination, and the base sequences of 16S rDNA of the strain of the present invention obtained therefrom are described in SEQ ID NO: 6. In addition, the sequence is compared with the 16S rDNA sequence of the γ-subclass of Pseudomonas genus strain and proteobacteria is shown in Table 1 below.

As a result, the strain of the present invention was identified as Pseudomonas aeruginosa with a homology of 99.9%, and the strain was deposited by the inventors to the Biotechnology Research Institute Gene Bank on August 4, 1999 ( Accession No .: KCTC 8953P).

Example 3 Isolation of Chromosome DNA from Pseudomonas eryuginosa

Genome DNA Separation Kit from Bio 101 (G NOME ^™) for separating chromosomes encoding esterases that specifically act on optically active (R) -carboxylic acid methyl esters from Pseudomonas irruginosa identified in Example 2 DNA isolation kit) was used. First, inoculated with Pseudomonas irruginosa separated in 5 ml of LB medium (10% bacto tryptone, 5% bacto-yeast extract, 10% sodium chloride, pH 7.0) and incubated at 30 ℃ for 24 hours. After sufficient growth of the cells, the cells are harvested by centrifugation for 5 minutes, and the obtained cell pellet is dissolved in cell suspension solution (10 mM Tris-Cl (pH 8.0), 0.1 M EDTA (pH 8.0)) to 1.85. ml of cell suspension was prepared. 50 μl of RNase solution and 100 μl of cell lysis / denaturation solution (0.5% SDS) were added to the cell suspension, followed by well mixing and incubation at 55 ° C. for 15 minutes. Thereafter, 25 μl of protease was mixed and reacted at 55 ° C. for 1 hour to remove the protein in the sample. 500 μl of dialysis buffer was added thereto, the sample was divided into 1.5 ml tubes, and cooled at 4 ° C. for 10 minutes. The pellet was then centrifuged at 12,000 rpm for 10 minutes to precipitate the pellet, and the supernatant was transferred to a 15 ml tube. DNA was precipitated by adding 2 ml of TE buffer (Tris-EDTA, pH 7.5) and 8 ml of 100% ethanol. Thereafter, the supernatant was discarded by centrifugation at 12,000 rpm for 15 minutes, and the DNA was dried in air and dissolved by adding TE buffer to the dried DNA. The DNA was partially cleaved with restriction enzyme Sau3 A and electrophoresed using a 1% agarose gel, and the DNA fragment was eluted from the gel to obtain a genomic DNA library of Pseudomonas irruginosa.

Example 4 Preparation of Recombinant Plasmids

As in Example 3, chromosome DNA was extracted from Pseudomonas irruginosa, and then partially digested with restriction enzyme Sau 3A1. This was previously inserted into the cloning vector pBluescript KSII + (Stratagene, USA) cut with the restriction enzyme Bam H I and introduced into E. coli DH5α (Stratagene, USA). In order to select a strain containing a gene encoding an esterase from the transformants, the following selection experiment was performed.

First, the transformants were agar medium containing tributyrin (tributyrin), a substrate for measuring enzyme activity of lipase (tributyrin 10g / l, agar 15g / l, tryptone 10g / l, yeast extract 5g / l, sodium chloride 10 g / l) was incubated and cultured, and a strain of tributyrin decomposed to form a transparent ring around the colonies was selected first. These were again agar medium containing 1 v / v% of (R, S) -acetylmercaptoisobutyric acid methyl ester used as an esterase substrate (v / v of (R, S) -acetylmercaptoisobutyric acid methyl ester). %, Agar 15g / l, tryptone 10g / l, yeast extract 5g / l, sodium chloride 10g / l), and only the second strain was selected to change the color around the colony yellow. Finally, a strain producing (R) -acetylmercaptoisobutyrate was selected using (R, S) -acetylmercaptoisobutyl acid methyl ester, which is the actual esterase reaction substrate. Analysis of the produced (R) -acetylmercaptoisobutyrate included gas chromatography (HEWLETT PACKARD 5890) and high performance liquid chromatography (HPLC, Chirex (R) NGLY DNB, Phenomenex, USA), 20 mM Ammonium acetate / methanol, Younglin, Korea] was used.

Through the above procedure, a transformant containing pTBL7, a 4.5 kb plasmid having (R) -acetylmercaptoisobutyrate production activity, was isolated.

Example 5 Isolation, Analysis, and Subcloning of Recombinant Plasmids

A schematic cloning procedure of the gene encoding the esterase is shown in FIG. 1 . DNA extraction from transformed E. coli was carried out using a common boiling method (Sambrook et al. , Molecular cloning, 1989) and an extraction method using a plasmid midi kit (Qiagen, USA). Kpn I, Bam HI, Nhe I, Nru I, Nco I, Sca I, etc.), and then subjected to electrophoresis using 0.8-1% agarose gel.

The restriction map and the enzyme position analysis of the inserted gene are shown in FIG. 2 . In FIG. 2 , pTBL7, pTBL71, and pTBL72 are inserted into pBluescript (R) SKII + vector, and other inserts are inserted into pUC119 cloning vector (Stratagene, USA).

Cutting the pTBL7 of 4.5 kb with restriction enzymes Kpn I and each DNA fragment of (R) - acetyl mercapto toy small butyrate production active-acetyl mercapto toy small research production activity of butyrate result, pTBL72 (R) from the 2.6 kb It appeared that the desired esterase exists.

Subsequently, pTBL72 was cleaved with restriction enzymes Bam HI, Nhe I, Nru I and subcloned. As a result, it was confirmed that pTBL76 cleaved with Nhe I and Nru I had a production capacity of (R) -acetylmercaptoisobutyrate. DNA inserts contained in pTBL76 were found to be the smallest sites with the capacity to produce (R) -acetylmercaptoisobutyrate. It has also been found that the size of the DNA encoding the esterase having the ability to produce (R) -acetylmercaptoisobutyrate is within about 1.1-kb.

Example 6 Base Sequence of Cloned Esterase Gene and Amino Acid Sequence Inferred from It

In order to analyze the nucleic acid base sequence of pTBL72, a DNA ladder having a size reduced to about 300-400 bp was prepared stepwise and subjected to sequencing to obtain a base sequence of about 2455 bp. Sequencing was performed using an automatic sequencing machine (ABI PRISM 377 autosequencer, Perkin-Elmer, USA).

An open reading frame (ORF) of the 2455 bp sequence confirmed that one ORF was present, and the homology was examined through the BLAST search and the ORF was associated with esterases and lipases. It has been shown to have high homology. This was named est A and the nucleotide sequence was registered with US GenBank under accession number AF170828.

The esterase gene that produces the optically active (R) -carboxylic acid isolated from the above is composed of 948 nucleotide sequences consisting of the sequence from 288th base to 1236th base of SEQ ID NO: 1. Esterase is an enzyme consisting of 316 amino acids. The guanine / cytosine ratio (G + C ratio) in the total sequence of the gene was 67.41%, the molecular weight was about 35 kDa, and the isoelectric point was investigated at pH 6.4. The esterase was found to be a newer enzyme that is larger in size than previously reported esterase derived from Pseudomonas fluorescens or Pseudomonas putida, and has an amino acid sequence different from these enzymes.

3A and 3B , triacylglycerol lipase and Acinetobacter calcoaceticus derived from Moraxella sp., Psychrobacter immobilis , and Acinetobacter calcoaceticus As a result of comparing the homology of the carboxyl esterase derived from the amino acid sequence, glycine-X-serine-X-glycine (GXSXG) containing serine, the 169th amino acid of the newly isolated esterase in the present invention. Consensus sequences were all present. The serine residue is known as the center of an enzyme activity such as esterase. 3A and 3B , the amino acid sequence in the solid box indicates the amino acid sequence (-HG- and -GXSXG-) having homology with known serine esterases, and the gray and dark gray portions represent other amino acid sequences. The higher homology is shown, and the higher homology is represented by the shade of black.

In addition, another consensus sequence of histidine-glysine (His-Gly), which assists the activity of the sequence, is positioned about 70 amino acids from the serine residue of the consensus sequence including the serine, thereby exhibiting typical serine esterase properties. It can be seen that the esterase of the present invention is a kind of serine esterase.

Example 7 Development of Transgenic E. Coli Strain Highly Expressing Recombinant Esterase

In order to prepare an expression vector containing the estA gene, the expression vector pES22b was prepared by inserting the estA gene of SEQ ID NO: 1 into the restriction enzymes Nco I and Bam HI sites of pET22b (Novagen, USA).

First, in order to facilitate the purification of the expressed esterase, a polymerase chain reaction was carried out using plasmid pTBL74 as a template. The estA gene N-terminal primer and C-terminal primer each have a restriction enzyme cleavage site of Nco I, an oligonucleotide represented by SEQ ID NO: 4 and a restriction enzyme cleavage site of Bam HI, and a nucleotide sequence described by SEQ ID NO: 5 Oligonucleotides were used. In the case of the C-terminal primer, it was designed to contain a base sequence encoding histidine so that 6 histidines could be added. PCR was repeated 30 times in a cycle consisting of 1 minute at 94 ° C, 1 minute at 58 ° C, and 1 minute at 72 ° C.

In the above reaction, a large amount of DNA fragments designed to connect six histidines (His) to the C-terminus of the est A gene was extracted in a Qiagen gel elution kit (Quiagen, USA). Was inserted into the DNA fragment in the NcoI and BamHI restriction sites of the pET22b vector (Novagen, USA), it is shown the restriction map in Fig. The recombinant plasmid pES22b was mixed with E. coli BL21 (Invitrogen, USA) competent cells and left for 30 minutes on ice and heat shock was applied at 42 ° C. for 30 seconds to prepare a transformed strain. The transformant was named BL21 PES and deposited with the Biotechnology Research Institute Gene Bank on August 4, 1999 (Accession No .: KCTC 8952P).

Example 8 Expression of Esterase in Recombinant Escherichia Coli

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to investigate the expression patterns of the est A gene in the recombinant E. coli prepared in Example 7. First, 10% polyacrylamide gel (Biorad Co., USA) was installed on an electrophoresis device, and electrophoresis was performed by filling a mobile buffer solution (tris glycine buffer solution) in the electrophoresis device. First, E. coli BL21 PES containing pTBL72 containing est A was incubated at 37 ° C. using LB medium, and cultured after 1, 2 and 4 hours after inoculation, respectively, and centrifuged at 3000 rpm for 30 minutes. After the cells were recovered by centrifugation, 0.2-fold volume of cell disruption buffer solution (50 mM sodium phosphate buffer, pH 7.8, 300 mM sodium chloride, Quiagen, USA) was added to form a 5-fold suspension. The cells were crushed by using an ultrasonic crusher, centrifuged, 50 μl of the supernatant containing esterase was mixed with 50 μl of sample buffer, pretreated for 5 minutes at 95 ° C., and centrifuged at 10,000 rpm for 3-4 minutes. Centrifuged supernatants were loaded into the wells with a molecular weight standard of 20 μl and electrophoresed at a voltage of 120V. When the dye line developed to the bottom of the gel, electrophoresis was stopped, the gel was taken out, and stained with Coomassie Brilliant Blue. As a control, E. coli protein without the est A gene was used, and the results are shown in FIG. 5 .

As a result, in the control group, almost no band of 36,400 Daltons, the molecular weight inferred from the amino acid sequence of the esterase, appeared, and the protein molecular weight in the sample was about 1, 2, 3, and 4 hours after the expression of the esterase. The dark band at the 35,000 dalton site showed that the esterase was effectively produced. It was also confirmed that this protein band was an esterase because its molecular weight was very close to the molecular weight deduced from the amino acid sequence.

Example 9 Investigation of Activity of Recombinant Esterase

Chemically, to produce (R) -acetylmercaptoisobutyrate from (R, S) -acetylmercaptoisobutyl acid methyl ester, the (S) form is produced as a mixed racemate. Therefore, the esterase produced by the recombinant E. coli of Example 7 produced a carboxylic acid having pure optical activity of only (R) or (S) type, not racemate of type (R) and (S). In order to check whether the optical activity of the material produced by gas chromatography was investigated. Chemically synthesized (R) and (S) acetylmertopisobutyrate diesters as a standard, and the GC peak and the dies of acetylmercaptoisobutyrate produced by the recombinant E. coli of Example 7 The peaks of the stereomers are compared and shown in FIG. 6 . As a result, as can be seen in Figure 6 it can be seen that the acetylmercaptoisobutyrate produced by the recombinant esterase (R) type.

Example 10 Thermal Stability of Recombinant Esterase

The thermal stability of Pseudomonas irruginosa-derived esterase produced by the recombinant E. coli BL21 PES prepared in Example 7 was investigated as follows. First, E. coli BL21 PES containing pTBL72 containing est A was incubated at 37 ° C. for 24 hours using LB medium, and the cells were recovered by centrifugation. Then, 0.2-fold volume of cell disruption buffer solution (50 mM sodium phosphate buffer) was used. Solution, pH 7.8, 300 mM sodium chloride, Quiagen, USA) was added to form a 5-fold concentrated suspension. The cells were crushed by using an ultrasonic crusher, centrifuged, and thermal stability was investigated using a supernatant containing esterase. That is, after maintaining for 1 hour at 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, the activity of the esterase at 30 ℃ was investigated. Esterase activity was determined by gas chromatography measuring the amount of (R) -acetylmercaptoisobutyrate produced, expressed as activity per mg of dry cell weight (DCW), and the results are shown in Table 2 below. Shown in

Thermal Stability of Esterases Produced in Transformants Temperature (℃) Active (U / mg DCW) 30 404.09 40 426.36 50 438.63 60 429.09 70 420.91

As can be seen in Table 2 , the recombinant esterase of the present invention showed little change in activity due to temperature change, and showed very excellent thermal stability because the activity was hardly decreased even at a high temperature of 70 ° C.

Novel esterases derived from Pseudomonas irruginosa of the present invention have an excellent ability to produce optically active carboxylic acids from carboxylic ester racemates and exhibit stability to heat even at high temperatures of 70 ° C. or higher. In particular, it can be usefully used in the production of high blood pressure treatment agents such as meptopril and analapril, and has a high reaction selectivity compared to the production of optically active carboxylic acids by conventional chemical synthesis, and a simple process and environmental pollutants. There are advantages such as low emissions.

Claims (11)

Esterases having an amino acid sequence as set forth in SEQ ID NO: 2 and selectively producing optically active carboxylic acids and their enantiomeric esters by asymmetrically hydrolyzing carboxylic ester racemates. The esterase according to claim 1, which produces an optically active carboxylic acid represented by the following Chemical Formula 1. Formula 1 Wherein R ₁ is alkyl, aralkyl or aryl, R ₂ is alkyl and n is 1 or 2. The esterase according to claim 1, wherein the optically active carboxylic acid is of type (R). Esterase gene having a nucleotide sequence set forth in SEQ ID NO: 1, encoding the esterase of claim 1. Esterase gene, comprising the nucleotide sequence set forth in SEQ ID NO: 3, encoding the esterase of claim 1. An expression vector comprising the esterase gene of claim 5. The expression vector pES22b of Claim 6 represented by the restriction map of FIG. E. coli transformants transformed with the expression vector of claim 6. The transformant BL21 PES (KCTC 8952P) according to claim 8. A process for producing an optically active carboxylic acid from a carboxylic ester racemate using the esterase of claim 1. Pseudomonas aeruginosa (KCTC 8953P), which produces the esterase of claim 1.