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Zhang Z, Long M, Zheng N, Deng Y, Wang Q, Osire T, Xia X. Redesign of γ-glutamyl transpeptidase from Bacillus subtilis for high-level production of L-theanine by cavity topology engineering. Appl Microbiol Biotechnol 2023; 107:3551-3564. [PMID: 37099056 DOI: 10.1007/s00253-023-12544-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2023] [Revised: 04/12/2023] [Accepted: 04/16/2023] [Indexed: 04/27/2023]
Abstract
L-Theanine is a multifunctional nonprotein amino acid found naturally in tea leaves. It has been developed as a commercial product for a wide range of applications in the food, pharmaceutical, and healthcare industries. However, L-theanine production catalyzed by γ-glutamyl transpeptidase (GGT) is limited by the low catalytic efficiency and specificity of this class of enzymes. Here, we developed a strategy for cavity topology engineering (CTE) based on the cavity geometry of GGT from B. subtilis 168 (CGMCC 1.1390) to obtain an enzyme with high catalytic activity and applied it to the synthesis of L-theanine. Three potential mutation sites, M97, Y418, and V555, were identified using the internal cavity as a probe, and residues G, A, V, F, Y, and Q, which may affect the shape of the cavity, were obtained directly by computer statistical analysis without energy calculations. Finally, 35 mutants were obtained. The optimal mutant Y418F/M97Q showed a 4.8-fold improvement in catalytic activity and a 25.6-fold increase in catalytic efficiency. The recombinant enzyme Y418F/M97Q exhibited a high space-time productivity of 15.4 g L-1 h-1 by whole-cell synthesis in a 5 L bioreactor, which was one of the highest concentrations reported so far at 92.4 g L-1. Overall, this strategy is expected to enhance the enzymatic activity associated with the synthesis of L-theanine and its derivatives.Key points • Cavity topology engineering was used to modify the GGT for L-theanine biocatalysis. • The catalytic efficiency of GGT was increased by 25.6-fold. • Highest productivity of L-theanine reached 15.4 g L -1 h-1 (92.4 g L-1) in a 5 L bioreactor.
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Affiliation(s)
- Zehua Zhang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Mengfei Long
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Nan Zheng
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Yu Deng
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Qiong Wang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China
| | - Tolbert Osire
- Faculty of Biology, Shenzhen MSU-BIT University, Shenzhen, 518172, Guangdong, China
| | - Xiaole Xia
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi, 214122, Jiangsu, China.
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2
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Nguyen L, Schultz DC, Terzyan SS, Rezaei M, Songb J, Li C, You Y, Hanigan MH. Design and evaluation of novel analogs of 2-amino-4-boronobutanoic acid (ABBA) as inhibitors of human gamma-glutamyl transpeptidase. Bioorg Med Chem 2022; 73:116986. [PMID: 36208545 DOI: 10.1016/j.bmc.2022.116986] [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: 06/17/2022] [Revised: 08/19/2022] [Accepted: 08/19/2022] [Indexed: 11/29/2022]
Abstract
Inhibitors of gamma-glutamyl transpeptidase (GGT1, aka gamma-glutamyl transferase) are needed for the treatment of cancer, cardiovascular illness and other diseases. Compounds that inhibit GGT1 have been evaluated in the clinic, but no inhibitor has successfully demonstrated specific and systemic GGT1 inhibition. All have severe side effects. L-2-amino-4‑boronobutanoic acid (l-ABBA), a glutamate analog, is the most potent GGT1 inhibitor in vitro. In this study, we have solved the crystal structure of human GGT1 (hGGT1) with ABBA bound in the active site. The structure was interrogated to identify interactions between the enzyme and the inhibitor. Based on these data, a series of novel ABBA analogs were designed and synthesized. Their inhibitory activity against the hydrolysis and transpeptidation activities of hGGT1 were determined. The lead compounds were crystalized with hGGT1 and the structures solved. The kinetic data and structures of the complexes provide new insights into the critical role of protein structure dynamics in developing compounds for inhibition of hGGT1.
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Affiliation(s)
- Luong Nguyen
- Department of Pharmaceutical Sciences, The State University of New York at Buffalo, Buffalo, NY 14214, United States
| | - Daniel C Schultz
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States
| | - Simon S Terzyan
- Laboratory of Biomolecular Structure and Function, Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States
| | - Mohammad Rezaei
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States
| | - Jinhua Songb
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States
| | - Chenglong Li
- Department of Medicinal Chemistry, University of Florida, Gainesville, FL 32610, United States
| | - Youngjae You
- Department of Pharmaceutical Sciences, The State University of New York at Buffalo, Buffalo, NY 14214, United States
| | - Marie H Hanigan
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, United States.
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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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4
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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: 25] [Impact Index Per Article: 8.3] [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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5
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Mutational Analysis of a Highly Conserved PLSSMXP Sequence in the Small Subunit of Bacillus licheniformis γ-Glutamyltranspeptidase. Biomolecules 2019; 9:biom9090508. [PMID: 31546955 PMCID: PMC6769717 DOI: 10.3390/biom9090508] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 01/13/2023] Open
Abstract
A highly conserved 458PLSSMXP464 sequence in the small subunit (S-subunit) of an industrially important Bacillus licheniformis γ-glutamyltranspeptidase (BlGGT) was identified by sequence alignment. Molecular structures of the precursor mimic and the mature form of BlGGT clearly reveal that this peptide sequence is in close spatial proximity to the self-processing and catalytic sites of the enzyme. To probe the role of this conserved sequence, ten mutant enzymes of BlGGT were created through a series of deletion and alanine-scanning mutagenesis. SDS-PAGE and densitometric analyses showed that the intrinsic ability of BlGGT to undergo autocatalytic processing was detrimentally affected by the deletion-associated mutations. However, loss of self-activating capacity was not obviously observed in most of the Ala-replacement mutants. The Ala-replacement mutants had a specific activity comparable to or greater than that of the wild-type enzyme; conversely, all deletion mutants completely lost their enzymatic activity. As compared with BlGGT, S460A and S461S showed greatly enhanced kcat/Km values by 2.73- and 2.67-fold, respectively. The intrinsic tryptophan fluorescence and circular dichroism spectral profiles of Ala-replacement and deletion mutants were typically similar to those of BlGGT. However, heat and guanidine hydrochloride-induced unfolding transitions of the deletion-associated mutant proteins were severely reduced as compared with the wild-type enzyme. The predictive mutant models suggest that the microenvironments required for both self-activation and catalytic reaction of BlGGT can be altered upon mutations.
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Hibi T, Imaoka M, Shimizu Y, Itoh T, Wakayama M. Crystal structure analysis and enzymatic characterization of γ-glutamyltranspeptidase from Pseudomonas nitroreducens. Biosci Biotechnol Biochem 2019; 83:262-269. [DOI: 10.1080/09168451.2018.1547104] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
ABSTRACT
Theanine (γ-glutamylethylamide) is an amino acid analog that reduces blood pressure and improves immune responses. The ϒ-glutamyltranspeptidase (GGT) from Pseudomonas nitroreducens IFO12694 (PnGGT) has a unique preference for primary amines as ϒ-glutamyl acceptors over standard L-amino acids and peptides. This characteristic is useful for the synthesis of theanine. We used X-ray crystallographic analysis to understand the structural basis of PnGGT’s hydrolysis and transpeptidation reactions and to characterize its previously unidentified acceptor site. Structural studies of PnGGT have shown that key interactions between three residues (Trp385, Phe417, and Trp525) distinguish PnGGT from other GGTs. We studied the roles of these residues in the distinct biochemical properties of PnGGT using site-directed mutagenesis. All mutants showed a significant decrease in hydrolysis activity and an increase in transpeptidase activity, suggesting that the aromatic side chains of Trp385, Phe417, and Trp525 were involved in the recognition of acceptor substrates.
Abbreviations: ϒ-glutamyl peptide, theanine, X-ray crystallography.
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Affiliation(s)
- Takao Hibi
- Department of Bioscience and Biotechnology, Fukui Prefectural University, Fukui, Japan
| | - Masashi Imaoka
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Yoichiro Shimizu
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
| | - Takafumi Itoh
- Department of Bioscience and Biotechnology, Fukui Prefectural University, Fukui, Japan
| | - Mamoru Wakayama
- Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga, Japan
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7
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Liu T, Yan QL, Feng L, Ma XC, Tian XG, Yu ZL, Ning J, Huo XK, Sun CP, Wang C, Cui JN. Isolation of γ-Glutamyl-Transferase Rich-Bacteria from Mouse Gut by a Near-Infrared Fluorescent Probe with Large Stokes Shift. Anal Chem 2018; 90:9921-9928. [DOI: 10.1021/acs.analchem.8b02118] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Tao Liu
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
| | - Qiu-Long Yan
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Lei Feng
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
- Institute of Functional Materials and Molecular Imaging, College of Emergency and Trauma, Hainan Medical University, Haikou 571199, China
| | - Xiao-Chi Ma
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Xiang-Ge Tian
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Zhen-Long Yu
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Jing Ning
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Xiao-Kui Huo
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Cheng-Peng Sun
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Chao Wang
- College of Pharmacy, Academy of Integrative Medicine, Department of Biochemistry and Molecular Biology, Dalian Medical University, Dalian 116044, China
| | - Jing-Nan Cui
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
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Abstract
Many potentially toxic electrophilic xenobiotics and some endogenous compounds are detoxified by conversion to the corresponding glutathione S-conjugate, which is metabolized to the N-acetylcysteine S-conjugate (mercapturate) and excreted. Some mercapturate pathway components, however, are toxic. Bioactivation (toxification) may occur when the glutathione S-conjugate (or mercapturate) is converted to a cysteine S-conjugate that undergoes a β-lyase reaction. If the sulfhydryl-containing fragment produced in this reaction is reactive, toxicity may ensue. Some drugs and halogenated workplace/environmental contaminants are bioactivated by this mechanism. On the other hand, cysteine S-conjugate β-lyases occur in nature as a means of generating some biologically useful sulfhydryl-containing compounds.
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Kumari S, Pal RK, Gupta R, Goel M. High Resolution X-ray Diffraction Dataset for Bacillus licheniformis Gamma Glutamyl Transpeptidase-acivicin complex: SUMO-Tag Renders High Expression and Solubility. Protein J 2017; 36:7-16. [PMID: 28120227 DOI: 10.1007/s10930-017-9693-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Gamma glutamyl transpeptidase, (GGT) is a ubiquitous protein which plays a central role in glutathione metabolism and has myriad clinical implications. It has been shown to be a virulence factor for pathogenic bacteria, inhibition of which results in reduced colonization potential. However, existing inhibitors are effective but toxic and therefore search is on for novel inhibitors, which makes it imperative to understand the interactions of various inhibitors with the protein in substantial detail. High resolution structures of protein bound to different inhibitors can serve this purpose. Gamma glutamyl transpeptidase from Bacillus licheniformis is one of the model systems that have been used to understand the structure-function correlation of the protein. The structures of the native protein (PDB code 4OTT), of its complex with glutamate (PDB code 4OTU) and that of its precursor mimic (PDB code 4Y23) are available, although at moderate/low resolution. In the present study, we are reporting the preliminary analysis of, high resolution X-ray diffraction data collected for the co-crystals of B. licheniformis, Gamma glutamyl transpeptidase, with its inhibitor, Acivicin. Crystals belong to the orthorhombic space group P212121 and diffract X-ray to 1.45 Å resolution. This is the highest resolution data reported for all GGT structures available till now. The use of SUMO fused expression system enhanced yield of the target protein in the soluble fraction, facilitating recovery of protein with high purity. The preliminary analysis of this data set shows clear density for the inhibitor, acivicin, in the protein active site.
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Affiliation(s)
- Shobha Kumari
- Department of Biophysics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Ravi Kant Pal
- National Institute of Immunology (NII), Aruna Asaf Ali Marg, New Delhi, 110067, India
| | - Rani Gupta
- Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India
| | - Manisha Goel
- Department of Biophysics, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India.
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10
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Oliveira de Souza J, Dawson A, Hunter WN. An Improved Model of the Trypanosoma brucei CTP Synthetase Glutaminase Domain-Acivicin Complex. ChemMedChem 2017; 12:577-579. [PMID: 28333400 PMCID: PMC5413811 DOI: 10.1002/cmdc.201700118] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Revised: 03/21/2017] [Indexed: 11/17/2022]
Abstract
The natural product acivicin inhibits the glutaminase activity of cytidine triphosphate (CTP) synthetase and is a potent lead compound for drug discovery in the area of neglected tropical diseases, specifically trypanosomaisis. A 2.1-Å-resolution crystal structure of the acivicin adduct with the glutaminase domain from Trypanosoma brucei CTP synthetase has been deposited in the RCSB Protein Data Bank (PDB) and provides a template for structure-based approaches to design new inhibitors. However, our assessment of that data identified deficiencies in the model. We now report an improved and corrected inhibitor structure with changes to the chirality at one position, the orientation and covalent structure of the isoxazoline moiety, and the location of a chloride ion in an oxyanion binding site that is exploited during catalysis. The model is now in agreement with established chemical principles and allows an accurate description of molecular recognition of the ligand and the mode of binding in a potentially valuable drug target.
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Affiliation(s)
- Juliana Oliveira de Souza
- Division of Biological Chemistry and Drug DiscoveryCollege of Life SciencesUniversity of DundeeDundeeDD1 5EHScotlandUK
| | - Alice Dawson
- Division of Biological Chemistry and Drug DiscoveryCollege of Life SciencesUniversity of DundeeDundeeDD1 5EHScotlandUK
| | - William N. Hunter
- Division of Biological Chemistry and Drug DiscoveryCollege of Life SciencesUniversity of DundeeDundeeDD1 5EHScotlandUK
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Kreuzer J, Bach NC, Forler D, Sieber SA. Target discovery of acivicin in cancer cells elucidates its mechanism of growth inhibition†Electronic supplementary information (ESI) available: Synthesis, cloning, protein expression, purification and biochemical assays. See DOI: 10.1039/c4sc02339k. Chem Sci 2014; 6:237-245. [PMID: 25580214 PMCID: PMC4285139 DOI: 10.1039/c4sc02339k] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 09/09/2014] [Indexed: 12/13/2022] Open
Abstract
Using a chemical proteomic strategy we analyzed the targets of acivicin and provided a mechanistic explanation for its inhibition of cancer cell growth.
Acivicin is a natural product with diverse biological activities. Several decades ago its clinical application in cancer treatment was explored but failed due to unacceptable toxicity. The causes behind the desired and undesired biological effects have never been elucidated and only limited information about acivicin-specific targets is available. In order to elucidate the target spectrum of acivicin in more detail we prepared functionalized derivatives and applied them for activity based proteomic profiling (ABPP) in intact cancer cells. Target deconvolution by quantitative mass spectrometry (MS) revealed a preference for specific aldehyde dehydrogenases. Further in depth target validation confirmed that acivicin inhibits ALDH4A1 activity by binding to the catalytic site. In accordance with this, downregulation of ALDH4A1 by siRNA resulted in a severe inhibition of cell growth and might thus provide an explanation for the cytotoxic effects of acivicin.
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Affiliation(s)
- Johannes Kreuzer
- Center for Integrated Protein Science CIPSM , Institute of Advanced Studies IAS , Department Chemie , Lehrstuhl für Organische Chemie II , Technische Universität München , Lichtenbergstrasse 4 , 85747 Garching , Germany . ; ; Tel: +49 8928913302
| | - Nina C Bach
- Center for Integrated Protein Science CIPSM , Institute of Advanced Studies IAS , Department Chemie , Lehrstuhl für Organische Chemie II , Technische Universität München , Lichtenbergstrasse 4 , 85747 Garching , Germany . ; ; Tel: +49 8928913302
| | - Daniel Forler
- Bayer HealthCare Bayer Pharma AG , Müllerstr. 178 , 13353 Berlin , Germany
| | - Stephan A Sieber
- Center for Integrated Protein Science CIPSM , Institute of Advanced Studies IAS , Department Chemie , Lehrstuhl für Organische Chemie II , Technische Universität München , Lichtenbergstrasse 4 , 85747 Garching , Germany . ; ; Tel: +49 8928913302
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12
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Enzymatic synthesis of γ-glutamylmethylamide from glutamic acid γ-methyl ester and methylamine catalyzed by Escherichia coli having γ-glutamyltranspeptidase activity. Appl Biochem Biotechnol 2014; 173:851-6. [PMID: 24733529 DOI: 10.1007/s12010-014-0877-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2013] [Accepted: 03/24/2014] [Indexed: 10/25/2022]
Abstract
A new method for the synthesis of γ-glutamylmethylamide is presented. Glutamic acid γ-methyl ester was used as substrate for γ-glutamylmethylamide synthesis catalyzed by Escherichia coli with γ-glutamyltranspeptidase activity. Reaction conditions were optimized by using 300 mM glutamic acid γ-methyl ester and 3,000 mM methylamine at pH 10 and 40 °C. Bioconversion rate of γ-glutamylmethylamide reached 87 % after 10 h. γ-Glutamyltranspeptidase was reversibly inhibited only when glutamic acid γ-methyl ester was above 300 mM.
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