1
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Fan C, Qi J, Cong Y, Zhang C. Enhanced L-theanine production through semi-rational design of γ-glutamylmethylamide synthetase from Methylovorus mays. Enzyme Microb Technol 2024; 180:110481. [PMID: 39047348 DOI: 10.1016/j.enzmictec.2024.110481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2024] [Revised: 06/15/2024] [Accepted: 07/14/2024] [Indexed: 07/27/2024]
Abstract
The thermal instability of γ-glutamylmethylamide synthetase (GMAS) from Methylovorus mays has imposed limitations on its industrial applications, affecting both stability and activity at reaction temperatures. In this study, disulfide bridges were introduced through a combination of directed evolution and rational design to enhance GMAS stability. Among the variants that we generated, M12 exhibited a 1.46-fold improvement in relative enzyme activity and a 6.23-fold increase in half-life at 40℃ compared to the wild-type GMAS. Employing variant M12 under optimal conditions, we achieved the production of 645.7 mM (112.49 g/L) L-theanine with a productivity of 29.3 mM/h, from 800 mM substrate in an ATP regeneration system. Our strategy significantly enhances the biosynthesis efficiency of L-theanine by preserving the structural stability of the enzyme during the catalysis process.
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Affiliation(s)
- Chao Fan
- School of Biological Engineering, Dalian Polytechnic University, Dalian 116034, China; INNOBIO Corporation Limited, No. 49, DDA, Dalian 116600, China.
| | - Jiakun Qi
- School of Biological Engineering, Dalian Polytechnic University, Dalian 116034, China; INNOBIO Corporation Limited, No. 49, DDA, Dalian 116600, China.
| | - Yunhan Cong
- INNOBIO Corporation Limited, No. 49, DDA, Dalian 116600, China.
| | - Chunzhi Zhang
- School of Biological Engineering, Dalian Polytechnic University, Dalian 116034, China.
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2
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Cho DH, Kim S, Lee Y, Shin Y, Choi S, Oh J, Kim HT, Park SH, Park K, Bhatia SK, Yang YH. Enhanced theanine production with reduced ATP supply by alginate entrapped Escherichia coli co-expressing γ-glutamylmethylamide synthetase and polyphosphate kinase. Enzyme Microb Technol 2024; 175:110394. [PMID: 38277867 DOI: 10.1016/j.enzmictec.2024.110394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/11/2024] [Accepted: 01/11/2024] [Indexed: 01/28/2024]
Abstract
L-theanine is an amino acid with a unique flavor and many therapeutic effects. Its enzymatic synthesis has been actively studied and γ-Glutamylmethylamide synthetase (GMAS) is one of the promising enzymes in the biological synthesis of theanine. However, the theanine biosynthetic pathway with GMAS is highly ATP-dependent and the supply of external ATP was needed to achieve high concentration of theanine production. As a result, this study aimed to investigate polyphosphate kinase 2 (PPK2) as ATP regeneration system with hexametaphosphate. Furthermore, the alginate entrapment method was employed to immobilize whole cells containing both gmas and ppk2 together resulting in enhanced reusability of the theanine production system with reduced supply of ATP. After immobilization, theanine production was increased to 239 mM (41.6 g/L) with a conversion rate of 79.7% using 15 mM ATP and the reusability was enhanced, maintaining a 100% conversion rate up to the fifth cycles and 60% of conversion up to eighth cycles. It could increase long-term storage property for future uses up to 35 days with 75% activity of initial activity. Overall, immobilization of both production and cofactor regeneration system could increase the stability and reusability of theanine production system.
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Affiliation(s)
- Do Hyun Cho
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Suwon Kim
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Yeda Lee
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Yuni Shin
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Suhye Choi
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Jinok Oh
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea
| | - Hee Taek Kim
- Department of Food Science and Technology, Chungnam National University, Daejeon 34134, Republic of Korea
| | - See-Hyoung Park
- Department of Biological and Chemical Engineering, Hongik University, Sejong 30016, Republic of Korea
| | - Kyungmoon Park
- Department of Biological and Chemical Engineering, Hongik University, Sejong 30016, Republic of Korea
| | - Shashi Kant Bhatia
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Applications, Konkuk University, Seoul 05029, Republic of Korea
| | - Yung-Hun Yang
- Department of Biological Engineering, College of Engineering, Konkuk University, Gwangjin-gu, Seoul 05029, Republic of Korea; Institute for Ubiquitous Information Technology and Applications, Konkuk University, Seoul 05029, Republic of Korea.
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3
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Robescu MS, Alcántara AR, Calvio C, Morelli CF, Speranza G, Ubiali D, Bavaro T. l-Theanine Goes Greener: A Highly Efficient Bioprocess Catalyzed by the Immobilized γ-Glutamyl Transferase from Bacillus subtilis. CHEMSUSCHEM 2023; 16:e202202108. [PMID: 36655933 DOI: 10.1002/cssc.202202108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 01/18/2023] [Indexed: 06/17/2023]
Abstract
l-Theanine (l-Th) was synthesized by simply mixing the reactants (l-glutamine and ethylamine in water) at 25 °C and Bacillus subtilis γ-glutamyl transferase (BsGGT) covalently immobilized on glyoxyl-agarose according to a methodology previously reported by our research group; neither buffers, nor other additives were needed. Ratio of l-glutamine (donor) to ethylamine (acceptor), pH, enzymatic units (IU), and reaction time were optimized (molar ratio of donor/acceptor=1 : 8, pH 11.6, 1 IU mL-1 , 6 h), furnishing l-Th in 93 % isolated yield (485 mg, 32.3 g L-1 ) and high purity (99 %), after a simple filtration of the immobilized biocatalyst, distillation of the volatiles (unreacted ethylamine) and direct lyophilization. Immobilized BsGGT was re-used (four reaction cycles) with 100 % activity retention. This enzymatic synthesis represents a straightforward, fast, high-yielding, and easily scalable approach to l-Th preparation, besides having a favorable green chemistry metrics.
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Affiliation(s)
- Marina S Robescu
- Department of Drug Sciences, University of Pavia, viale Taramelli 12, Pavia, Italy
| | - Andrés R Alcántara
- Department of Chemistry in Pharmaceutical Sciences, Complutense University of Madrid, Plaza de Ramon y Cajal s/n, Madrid, Spain
| | - Cinzia Calvio
- Department of Biology and Biotechnology, University of Pavia, via Ferrata 1, Pavia, Italy
| | - Carlo F Morelli
- Department of Chemistry, University of Milan, via Golgi 19, Milano, Italy
| | - Giovanna Speranza
- Department of Chemistry, University of Milan, via Golgi 19, Milano, Italy
| | - Daniela Ubiali
- Department of Drug Sciences, University of Pavia, viale Taramelli 12, Pavia, Italy
| | - Teodora Bavaro
- Department of Drug Sciences, University of Pavia, viale Taramelli 12, Pavia, Italy
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4
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Senba H, Nishikawa A, Kimura Y, Tanaka S, Matsumoto JI, Doi M, Takenaka S. Improvement in salt-tolerance of Aspergillus oryzae γ-glutamyl transpeptidase via protein chimerization with Aspergillus sydowii homolog. Enzyme Microb Technol 2023; 167:110240. [PMID: 37084614 DOI: 10.1016/j.enzmictec.2023.110240] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2023] [Revised: 04/09/2023] [Accepted: 04/10/2023] [Indexed: 04/23/2023]
Abstract
γ-Glutamyl transpeptidase is one of the key enzymes involved in glutamate production during high-salt fermentation of soy sauce and miso by koji mold, Aspergillus oryzae. However, the activity of γ-glutamyl transpeptidase from A. oryzae (AOggtA) is markedly reduced in the presence of NaCl, thus classifying it as a non-salt-tolerant enzyme. In contrast, the homologous protein from the xerophilic mold, A. sydowii (ASggtA) maintains its activity under high-salt conditions. Therefore, in this study, a chimeric enzyme, ASAOggtA, was designed and engineered to improve salt-tolerance in AOggtA by swapping the N-terminal region, based on sequence and structure comparisons between salt-tolerant ASggtA and non-salt-tolerant AOggtA. The parental AOggtA and ASggtA and their chimera, ASAOggtA, were heterologously expressed in A. oryzae and purified. The chimeric enzyme inherited the superior activity and stability from each of the two parent enzymes. ASAOggtA showed > 2-fold greater tolerance than AOggtA in the presence of 18% NaCl. In addition, the chimera showed a broader range of pH stability and greater thermostability than ASggtA. AOggtA and ASAOggtA were sy over the range pH 3.0 to pH 10.5. Thermal stability was found to be in the order AOggtA (57.5 °C, t1/2 = 32.5 min) > ASAOggtA (55 °C, t1/2 = 20.5 min) > ASggtA (50 °C, t1/2 = 12.5 min). The catalytic and structural characteristics indicated that non-salt-tolerant AOggtA would not undergo irreversible structural changes in the presence of NaCl, but rather a temporary conformational change, which might result in reducing the substrate binding and catalytic activity, on the basis of kinetic properties. In addition, the chimeric enzyme showed hydrolytic activity toward L-glutamine that was as high as that of AOggtA. The newly-designed chimeric ASAOggtA might have potential applications in high-salt fermentation, such as miso and shoyu, to increase the content of the umami-flavor amino acid, L-glutamate.
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Affiliation(s)
- Hironori Senba
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan; Ozeki Corp, Gen Res Lab, 4-9 Imazu, Nishinomiya, Hyogo 6638227, Japan
| | - Arisa Nishikawa
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Yukihiro Kimura
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan
| | - Shinichi Tanaka
- Marutomo Co., Ltd, 1696 Kominato, Iyo, Ehime 799-3192, Japan
| | | | - Mikiharu Doi
- Marutomo Co., Ltd, 1696 Kominato, Iyo, Ehime 799-3192, Japan
| | - Shinji Takenaka
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501, Japan.
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Nishikawa A, Senba H, Kimura Y, Yokota S, Doi M, Takenaka S. Isolation and characterization of a salt-tolerant γ-glutamyl transpeptidase from xerophilic Aspergillus sydowii. 3 Biotech 2022; 12:253. [PMID: 36060894 PMCID: PMC9433638 DOI: 10.1007/s13205-022-03259-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 05/08/2022] [Indexed: 11/01/2022] Open
Abstract
Xerophilic Aspergillus molds isolated from halo-alkaliphilic and dry environments are attractive genetic resources for obtaining salt- and osmo-adaptive enzymes. A. sydowii MA0196 secreted the largest amount of γ-glutamyl transpeptidase (GGT) during solid-state fermentation at a low initial water activity (a w = 0.85). Gel filtration analysis revealed that the molecular mass of the purified native enzyme (MA0196 GGT) was 120 kDa. SDS-PAGE analysis showed that MA0196 GGT consists of two subunits with molecular masses of 56.4 and 33 kDa, indicating production from a proenzyme via autoproteolysis. Deglycosylation of the subunits by N-glycosidase F yielded 40.9 and 19.6 kDa species. MA0196 GGT retained transpeptidase and hydrolysis activities and their catalytic efficiency (k cat/K m) under high salt and low water activity. The enzyme displayed broad substrate specificity toward γ-glutamyl acceptors such as amino acids and the imidazole dipeptides, carnosine and anserine. Carnosine and L-glutamine were converted into γ-glutamyl-β-alanyl-L-histidine by MA0196 GGT with a 32.9% yield in the presence of 2% (v/v) dimethyl sulfoxide. Phylogenetic analysis indicated that MA0196 GGT forms a distinct lineage from A. oryzae and A. sojae GGTs. These excellent properties indicate that MA0196 GGT can be used in salted fermentation and for producing bioactive peptides. Supplementary Information The online version contains supplementary material available at 10.1007/s13205-022-03259-3.
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Affiliation(s)
- Arisa Nishikawa
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501 Japan
| | - Hironori Senba
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501 Japan
- Gen Res Lab, Ozeki Corp, 4-9 Imazu, Nishinomiya, Hyogo 663-8227 Japan
| | - Yukihiro Kimura
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501 Japan
| | - Satoko Yokota
- Marutomo Co., Ltd, 1696 Kominato, Iyo, Ehime 799-3192 Japan
| | - Mikiharu Doi
- Marutomo Co., Ltd, 1696 Kominato, Iyo, Ehime 799-3192 Japan
| | - Shinji Takenaka
- Division of Agrobioscience, Graduate School of Agricultural Science, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe 657-8501 Japan
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6
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Lin LL, Lu BY, Chi MC, Huang YF, Lin MG, Wang TF. Activation and thermal stabilization of a recombinant γ-glutamyltranspeptidase from Bacillus licheniformis ATCC 27811 by monovalent cations. Appl Microbiol Biotechnol 2022; 106:1991-2006. [PMID: 35230495 DOI: 10.1007/s00253-022-11836-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2021] [Revised: 02/08/2022] [Accepted: 02/12/2022] [Indexed: 12/27/2022]
Abstract
The regulation of enzyme activity through complexation with certain metal ions plays an important role in many biological processes. In addition to divalent metals, monovalent cations (MVCs) frequently function as promoters for efficient biocatalysis. Here, we examined the effect of MVCs on the enzymatic catalysis of a recombinant γ-glutamyltranspeptidase (BlrGGT) from Bacillus licheniformis ATCC 27,811 and the application of a metal-activated enzyme to L-theanine synthesis. The transpeptidase activity of BlrGGT was enhanced by Cs+ and Na+ over a broad range of concentrations with a maximum of 200 mM. The activation was essentially independent of the ionic radius, but K+ contributed the least to enhancing the catalytic efficiency. The secondary structure of BlrGGT remained mostly unchanged in the presence of different concentrations of MVCs, but there was a significant change in its tertiary structure under the same conditions. Compared with the control, the half-life (t1/2) of the Cs+-enriched enzyme at 60 and 65 °C was shown to increase from 16.3 and 4.0 min to 74.5 and 14.3 min, respectively. The simultaneous addition of Cs+ and Mg2+ ions exerted a synergistic effect on the activation of BlrGGT. This was adequately reflected by an improvement in the conversion of substrates to L-theanine by 3.3-15.1% upon the addition of 200 mM MgCl2 into a reaction mixture comprising the freshly desalted enzyme (25 μg/mL), 250 mM L-glutamine, 600 mM ethylamine, 200 mM each of the MVCs, and 50 mM borate buffer (pH 10.5). Taken together, our results provide interesting insights into the complexation of MVCs with BlrGGT and can therefore be potentially useful to the biocatalytic production of naturally occurring γ-glutamyl compounds. KEY POINTS: • The transpeptidase activity of B. licheniformis γ-glutamyltranspeptidase can be activated by monovalent cations. • The thermal stability of the enzyme was profoundly increased in the presence of 200 mM Cs+. • The simultaneous addition of Cs+and Mg2+ions to the reaction mixture improves L-theanine production.
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Affiliation(s)
- Long-Liu Lin
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Bo-Yuan Lu
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Meng-Chun Chi
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Yu-Fen Huang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan
| | - Min-Guan Lin
- Institute of Molecular Biology, Academia Sinica, Nangang District, Taipei City, 11529, Taiwan
| | - Tzu-Fan Wang
- Department of Applied Chemistry, National Chiayi University, 300 Syuefu Road, Chiayi City, 60004, Taiwan.
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7
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Sharma E, Lal MK, Gulati A, Gulati A. Heterologous expression, on-column refolding and characterization of gamma-glutamyl transpeptidase gene from Bacillus altitudinis IHB B1644: A microbial bioresource from Western Himalayas. Process Biochem 2022. [DOI: 10.1016/j.procbio.2022.02.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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8
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Saini M, Kalra S, Kaushik JK, Gupta R. Functional characterization of the extra sequence in the large subunit of γ-glutamyl transpeptidase from Bacillus atrophaeus: Role in autoprocessing and activity. Process Biochem 2021. [DOI: 10.1016/j.procbio.2021.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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9
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Production of l-Theanine by Escherichia coli in the Absence of Supplemental Ethylamine. Appl Environ Microbiol 2021; 87:AEM.00031-21. [PMID: 33741612 DOI: 10.1128/aem.00031-21] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 03/09/2021] [Indexed: 11/20/2022] Open
Abstract
l-Theanine is a nonproteinogenic amino acid present almost exclusively in tea plants and is beneficial for human health. For industrial production, l-theanine is enzymatically or chemically synthesized from glutamine/glutamate (or a glutamine/glutamate derivative) and ethylamine. Ethylamine is extremely flammable and toxic, which complicates and increases the cost of operational procedures. To solve these problems, we developed an artificial biosynthetic pathway to produce l-theanine in the absence of supplemental ethylamine. For this purpose, we identified and selected a novel transaminase (NCBI:protein accession number AAN70747) from Pseudomonas putida KT2440, which catalyzes the transamination of acetaldehyde to produce ethylamine, as well as γ-glutamylmethylamide synthetase (NCBI:protein accession number AAY37316) from Pseudomonas syringae pv. syringae B728a, which catalyzes the condensation of l-glutamate and ethylamine to produce l-theanine. Expressing these genes in Escherichia coli W3110S3GK and enhancing the production capacity of acetaldehyde and l-alanine achieved successful production of l-theanine without ethylamine supplementation. Furthermore, the deletion of ggt, which encodes γ-glutamyltranspeptidase (EC 2.3.2.2), achieved large-scale production of l-theanine by attenuating its decomposition. We show that an alanine decarboxylase-utilizing pathway represents a promising route for the fermentative production of l-theanine. Our study reports efficient methods to produce l-theanine in the absence of supplemental ethylamine.IMPORTANCE l-Theanine is widely used in food additives and dietary supplements. Industrial production of l-theanine uses the toxic and highly flammable precursor ethylamine, raising production costs. In this study, we used Escherichia coli to engineer two biosynthetic pathways that produce l-theanine from glucose and ammonia in the absence of supplemental ethylamine. This study establishes a foundation for safely and economically producing l-theanine.
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Saini M, Kashyap A, Bindal S, Saini K, Gupta R. Bacterial Gamma-Glutamyl Transpeptidase, an Emerging Biocatalyst: Insights Into Structure-Function Relationship and Its Biotechnological Applications. Front Microbiol 2021; 12:641251. [PMID: 33897647 PMCID: PMC8062742 DOI: 10.3389/fmicb.2021.641251] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 02/15/2021] [Indexed: 12/16/2022] Open
Abstract
Gamma-glutamyl transpeptidase (GGT) enzyme is ubiquitously present in all life forms and plays a variety of roles in diverse organisms. Higher eukaryotes mainly utilize GGT for glutathione degradation, and mammalian GGTs have implications in many physiological disorders also. GGTs from unicellular prokaryotes serve different physiological functions in Gram-positive and Gram-negative bacteria. In the present review, the physiological significance of bacterial GGTs has been discussed categorizing GGTs from Gram-negative bacteria like Escherichia coli as glutathione degraders and from pathogenic species like Helicobacter pylori as virulence factors. Gram-positive bacilli, however, are considered separately as poly-γ-glutamic acid (PGA) degraders. The structure-function relationship of the GGT is also discussed mainly focusing on the crystallization of bacterial GGTs along with functional characterization of conserved regions by site-directed mutagenesis that unravels molecular aspects of autoprocessing and catalysis. Only a few crystal structures have been deciphered so far. Further, different reports on heterologous expression of bacterial GGTs in E. coli and Bacillus subtilis as hosts have been presented in a table pointing toward the lack of fermentation studies for large-scale production. Physicochemical properties of bacterial GGTs have also been described, followed by a detailed discussion on various applications of bacterial GGTs in different biotechnological sectors. This review emphasizes the potential of bacterial GGTs as an industrial biocatalyst relevant to the current switch toward green chemistry.
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Affiliation(s)
| | | | | | | | - Rani Gupta
- Department of Microbiology, University of Delhi South Campus, New Delhi, India
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11
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Yang T, Liu S, Liu H, Long M, Chen P, Zhang X, Xu M, Rao Z. Semi-quantitative activity assays for high-throughput screening of higher activity gamma glutamyl transferase and enzyme immobilization to efficiently synthesize L-theanine. J Biotechnol 2021; 330:9-16. [PMID: 33636215 DOI: 10.1016/j.jbiotec.2021.02.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 11/25/2020] [Accepted: 02/18/2021] [Indexed: 11/17/2022]
Abstract
The bio-production of theanine is currently of significant interest due to its wide applications in food and healthcare products. Gamma glutamyl transferase (GGT) has been widely applied in L-theanine synthesis, but L-theanine yields remain prohibitively low for commercial production. In this study, a robust high-throughput screening process for isolating GGT mutants was developed through a combination of error-prone PCR techniques and a colorimetric reaction. The co-expression of PrsA lipoprotein enhances the secretion of GGT, thus GGT could be obtained quickly and easily without crushing cells. Random mutations on ggt genes were introduced by using error-prone PCR kits to build a large mutant library. A colorless compound generated by the reaction between NH4+ (released from L-theanine synthesis) and OPA was measured quantitatively by UV/visible spectroscopy when mixed with TCA and DMSO. Approximately 30 positive clones with improved color formation on the 96-well plates were identified, and mutants T413P and T463S with more than by 30 % higher transpeptidation activity versus the original GGT were isolated. To improve the operational stability and economical use, mutant GGT was immobilized on a prepared oxidized cellulose nanofiber membrane. The remaining activity of immobilized GGT was 88 % versus 72 % of free enzyme over 15 h. A fed-batch conversion was performed with the immobilized GGT, and over 70 g/L L-theanine could be accumulated within 18 h after feeding twice. Versus other studies, this is one of the best L-theanine synthesis systems using immobilized GGT.
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Affiliation(s)
- Taowei Yang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China.
| | - Shuanying Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China
| | - Huiling Liu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China
| | - Mengfei Long
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China
| | - Pengcheng Chen
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China
| | - Xian Zhang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China
| | - Meijuan Xu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China
| | - Zhiming Rao
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, Jiangsu Province 214122, China.
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