1
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Cooper AJL, Dorai T, Pinto JT, Denton TT. Metabolic Heterogeneity, Plasticity, and Adaptation to "Glutamine Addiction" in Cancer Cells: The Role of Glutaminase and the GTωA [Glutamine Transaminase-ω-Amidase (Glutaminase II)] Pathway. BIOLOGY 2023; 12:1131. [PMID: 37627015 PMCID: PMC10452834 DOI: 10.3390/biology12081131] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 07/06/2023] [Accepted: 07/21/2023] [Indexed: 08/27/2023]
Abstract
Many cancers utilize l-glutamine as a major energy source. Often cited in the literature as "l-glutamine addiction", this well-characterized pathway involves hydrolysis of l-glutamine by a glutaminase to l-glutamate, followed by oxidative deamination, or transamination, to α-ketoglutarate, which enters the tricarboxylic acid cycle. However, mammalian tissues/cancers possess a rarely mentioned, alternative pathway (the glutaminase II pathway): l-glutamine is transaminated to α-ketoglutaramate (KGM), followed by ω-amidase (ωA)-catalyzed hydrolysis of KGM to α-ketoglutarate. The name glutaminase II may be confused with the glutaminase 2 (GLS2) isozyme. Thus, we recently renamed the glutaminase II pathway the "glutamine transaminase-ω-amidase (GTωA)" pathway. Herein, we summarize the metabolic importance of the GTωA pathway, including its role in closing the methionine salvage pathway, and as a source of anaplerotic α-ketoglutarate. An advantage of the GTωA pathway is that there is no net change in redox status, permitting α-ketoglutarate production during hypoxia, diminishing cellular energy demands. We suggest that the ability to coordinate control of both pathways bestows a metabolic advantage to cancer cells. Finally, we discuss possible benefits of GTωA pathway inhibitors, not only as aids to studying the normal biological roles of the pathway but also as possible useful anticancer agents.
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Affiliation(s)
- Arthur J. L. Cooper
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA; (T.D.); (J.T.P.)
| | - Thambi Dorai
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA; (T.D.); (J.T.P.)
- Department of Urology, New York Medical College, Valhalla, NY 10595, USA
| | - John T. Pinto
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY 10595, USA; (T.D.); (J.T.P.)
| | - Travis T. Denton
- Department Pharmaceutical Sciences, College of Pharmacy & Pharmaceutical Sciences, Washington State University Health Sciences Spokane, Spokane, WA 99202, USA
- Department of Translational Medicine and Physiology, Elson S. Floyd College of Medicine, Washington State University Health Sciences Spokane, Spokane, WA 99164, USA
- Steve Gleason Institute for Neuroscience, Washington State University Health Sciences Spokane, Spokane, WA 99164, USA
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2
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The Rosetta Stone Hypothesis-Based Interaction of the Tumor Suppressor Proteins Nit1 and Fhit. Cells 2023; 12:cells12030353. [PMID: 36766695 PMCID: PMC9913352 DOI: 10.3390/cells12030353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/11/2023] [Accepted: 01/14/2023] [Indexed: 01/20/2023] Open
Abstract
In previous studies, we have identified the tumor suppressor proteins Fhit (fragile histidine triad) and Nit1 (Nitrilase1) as interaction partners of β-catenin both acting as repressors of the canonical Wnt pathway. Interestingly, in D. melanogaster and C. elegans these proteins are expressed as NitFhit fusion proteins. According to the Rosetta Stone hypothesis, if proteins are expressed as fusion proteins in one organism and as single proteins in others, the latter should interact physically and show common signaling function. Here, we tested this hypothesis and provide the first biochemical evidence for a direct association between Nit1 and Fhit. In addition, size exclusion chromatography of purified recombinant human Nit1 showed a tetrameric structure as also previously observed for the NitFhit Rosetta Stone fusion protein Nft-1 in C. elegans. Finally, in line with the Rosetta Stone hypothesis we identified Hsp60 and Ubc9 as other common interaction partners of Nit1 and Fhit. The interaction of Nit1 and Fhit may affect their enzymatic activities as well as interaction with other binding partners.
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3
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Epova EY, Shevelev AB, Shurubor YI, Cooper AJL, Biryukova YK, Bogdanova ES, Tyno YY, Lebedeva AA, Krasnikov BF. A novel efficient producer of human ω-amidase (Nit2) in Escherichia coli. Anal Biochem 2021; 632:114332. [PMID: 34391728 DOI: 10.1016/j.ab.2021.114332] [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: 04/10/2021] [Revised: 07/09/2021] [Accepted: 08/06/2021] [Indexed: 11/25/2022]
Abstract
Nit2/ω-amidase catalyzes the hydrolysis of α-ketoglutaramate (KGM, the α-keto acid analogue of glutamine) to α-ketoglutarate and ammonia. The enzyme also catalyzes the amide hydrolysis of monoamides of 4- and 5-C-dicarboxylates, including α-ketosuccinamate (KSM, the α-keto acid analogue of asparagine) and succinamate (SM). Here we describe an inexpensive procedure for high-yield expression of human Nit2 (hNit2) in Escherichia coli and purification of the expressed protein. This work includes: 1) the design of a genetic construct (pQE-Nit22) obtained from the previously described construct (pQE-Nit2) by replacing rare codons within an 81 bp-long DNA fragment "preferred" by E. coli near the translation initiation site; 2) methods for producing and maintaining the pQE-Nit22 construct; 3) purification of recombinant hNit2; and 4) activity measurements of the purified enzyme with KGM and SM. Important features of the hNit2 gene within the pQE-Nit22 construct are: 1) optimized codon composition, 2) the presence of an N-terminus His6 tag immediately after the initiating codon ATG (Met) that permits efficient purification of the end-product on a Ni-NTA-agarose column. We anticipate that the availability of high yield hNit2/ω-amidase will be helpful in elucidating the normal and pathological roles of this enzyme and in the design of specific inhibitors.
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Affiliation(s)
- Ekaterina Yu Epova
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, Russia
| | - Alexei B Shevelev
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia
| | | | - Arthur J L Cooper
- Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY, 10595, USA
| | - Yulia K Biryukova
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia
| | - Elena S Bogdanova
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia; Plekhanov Russian University of Economics, Moscow, Russia
| | - Yaroslav Ya Tyno
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia
| | - Anna A Lebedeva
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, Russia
| | - Boris F Krasnikov
- Centre for Strategic Planning of FMBA of the Russian Federation, Moscow, Russia; Department of Biochemistry and Molecular Biology, New York Medical College, Valhalla, NY, 10595, USA.
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4
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Silva Teixeira CS, Sousa SF, Cerqueira NMFSA. An Unsual Cys-Glu-Lys Catalytic Triad is Responsible for the Catalytic Mechanism of the Nitrilase Superfamily: A QM/MM Study on Nit2. Chemphyschem 2021; 22:796-804. [PMID: 33463886 DOI: 10.1002/cphc.202000751] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 01/13/2021] [Indexed: 12/29/2022]
Abstract
Nitrilase 2 (Nit2) is a representative member of the nitrilase superfamily that catalyzes the hydrolysis of α-ketosuccinamate into oxaloacetate. It has been associated with the metabolism of rapidly dividing cells like cancer cells. The catalytic mechanism of Nit2 employs a catalytic triad formed by Cys191, Glu81 and Lys150. The Cys191 and Glu81 play an active role during the catalytic process while the Lys150 is shown to play only a secondary role. The results demonstrate that the catalytic mechanism of Nit2 involves four steps. The nucleophilic attack of Cys191 to the α-ketosuccinamate, the formation of two tetrahedral enzyme adducts and the hydrolysis of a thioacyl-enzyme intermediate, from which results the formation of oxaloacetate and enzymatic turnover. The rate limiting step of the catalytic process is the formation of the first tetrahedral intermediate with a calculated activation free energy of 18.4 kcal/mol, which agrees very well with the experimental kcat (17.67 kcal/mol).
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Affiliation(s)
- Carla S Silva Teixeira
- UCIBIO@REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina, Universidade do Porto, Porto, 4200-319, Portugal
| | - Sérgio F Sousa
- UCIBIO@REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina, Universidade do Porto, Porto, 4200-319, Portugal
| | - Nuno M F S A Cerqueira
- UCIBIO@REQUIMTE, BioSIM, Departamento de Biomedicina, Faculdade de Medicina, Universidade do Porto, Porto, 4200-319, Portugal
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5
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Cyanide Hydratase Modification Using Computational Design and Docking Analysis for Improved Binding Affinity in Cyanide Detoxification. Molecules 2021; 26:molecules26061799. [PMID: 33806828 PMCID: PMC8004973 DOI: 10.3390/molecules26061799] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 03/11/2021] [Accepted: 03/15/2021] [Indexed: 01/08/2023] Open
Abstract
Cyanide is a hazardous and detrimental chemical that causes the inactivation of the respiration system through the inactivation of cytochrome c oxidase. Because of the limitation in the number of cyanide-degrading enzymes, there is a great demand to design and introduce new enzymes with better functionality. This study developed an integrated method of protein-homology-modelling and ligand-docking protein-design approaches that reconstructs a better active site from cyanide hydratase (CHT) structure. Designing a mutant CHT (mCHT) can improve the CHT performance. A computational design procedure that focuses on mutation for constructing a new model of cyanide hydratase with better activity was used. In fact, this study predicted the three-dimensional (3D) structure of CHT for subsequent analysis. Inducing mutation on CHT of Trichoderma harzianum was performed and molecular docking was used to compare protein interaction with cyanide as a ligand in both CHT and mCHT. By combining multiple designed mutations, a significant improvement in docking for CHT was obtained. The results demonstrate computational capabilities for enhancing and accelerating enzyme activity. The result of sequence alignment and homology modeling show that catalytic triad (Cys-Glu-Lys) was conserved in CHT of Trichoderma harzianum. By inducing mutation in CHT structure, MolDock score enhanced from −18.1752 to −23.8575, thus the nucleophilic attack can occur rapidly by adding Cys in the catalytic cavity and the total charge of protein in pH 6.5 is increased from −6.0004 to −5.0004. Also, molecular dynamic simulation shows a stable protein-ligand complex model. These changes would help in the cyanide degradation process by mCHT.
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6
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The metabolic importance of the glutaminase II pathway in normal and cancerous cells. Anal Biochem 2020; 644:114083. [PMID: 33352190 DOI: 10.1016/j.ab.2020.114083] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 12/08/2020] [Accepted: 12/15/2020] [Indexed: 02/08/2023]
Abstract
In rapidly dividing cells, including many cancer cells, l-glutamine is a major energy source. Utilization of glutamine is usually depicted as: l-glutamine → l-glutamate (catalyzed by glutaminase isozymes; GLS1 and GLS2), followed by l-glutamate → α-ketoglutarate [catalyzed by glutamate-linked aminotransferases or by glutamate dehydrogenase (GDH)]. α-Ketoglutarate is a major anaplerotic component of the tricarboxylic acid (TCA) cycle. However, the glutaminase II pathway also converts l-glutamine to α-ketoglutarate. This pathway consists of a glutamine transaminase coupled to ω-amidase [Net reaction: l-Glutamine + α-keto acid + H2O → α-ketoglutarate + l-amino acid + NH4+]. This review focuses on the biological importance of the glutaminase II pathway, especially in relation to metabolism of cancer cells. Our studies suggest a component enzyme of the glutaminase II pathway, ω-amidase, is utilized by tumor cells to provide anaplerotic carbon. Inhibitors of GLS1 are currently in clinical trials as anti-cancer agents. However, this treatment will not prevent the glutaminase II pathway from providing anaplerotic carbon derived from glutamine. Specific inhibitors of ω-amidase, perhaps in combination with a GLS1 inhibitor, may provide greater therapeutic efficacy.
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7
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Thakur N, Sharma N, Kumar V, Bhalla TC. Computational Analysis of the Primary and Secondary Structure of Amidases in Relation to their pH Adaptation. CURR PROTEOMICS 2020. [DOI: 10.2174/1570164616666190718150627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Background:
Amidases are ubiquitous enzymes and biological functions of these enzymes
vary widely. They are considered to be synergistically involved in the synthesis of a wide variety of
carboxylic acids, hydroxamic acids and hydrazides, which find applications in commodity chemicals
synthesis, pharmaceuticals agrochemicals and wastewater treatments.
Methods:
They hydrolyse a wide variety of amides (short-chain aliphatic amides, mid-chain amides,
arylamides, α-aminoamides and α-hydroxyamides) and can be grouped on the basis of their catalytic
site and preferred substrate. Despite their economic importance, we lack knowledge as to how these
amidases withstand elevated pH and temperature whereas others cannot.
Results:
The present study focuses on the statistical comparison between the acid-tolerant, alkali tolerant
and neutrophilic organisms. In silico analysis of amidases of acid-tolerant, alkali tolerant and neutrophilic
organisms revealed some striking trends as to how amino acid composition varies significantly.
Statistical analysis of primary and secondary structure revealed amino acid trends in amidases of
these three groups of bacteria. The abundance of isoleucine (Ile, I) in acid-tolerant and leucine (Leu, L)
in alkali tolerant showed the aliphatic amino acid dominance in extreme conditions of pH in acidtolerant
and alkali tolerant amidases.
Conclusion:
The present investigation insights physiochemical properties and dominance of some crucial
amino acid residues in the primary and secondary structure of some amidases from acid-tolerant,
alkali tolerant and neutrophilic microorganisms.
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Affiliation(s)
- Neerja Thakur
- Bioinformatics Centre, Himachal Pradesh University, Summer Hill, Shimla, Himachal Pradesh 171005, India
| | - Nikhil Sharma
- Bioinformatics Centre, Himachal Pradesh University, Summer Hill, Shimla, Himachal Pradesh 171005, India
| | - Vijay Kumar
- Department of Biotechnology, Himachal Pradesh University, Summer Hill, Shimla, Himachal Pradesh 171005, India
| | - Tek Chand Bhalla
- Department of Biotechnology, Himachal Pradesh University, Summer Hill, Shimla, Himachal Pradesh 171005, India
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8
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Krasnikov BF, Deryabina YI, Isakova EP, Biriukova IK, Shevelev AB, Antipov AN. New recombinant producer of human ω-amidase based on Escherichia coli. APPL BIOCHEM MICRO+ 2017. [DOI: 10.1134/s0003683817030115] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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9
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ω-Amidase: an underappreciated, but important enzyme in l-glutamine and l-asparagine metabolism; relevance to sulfur and nitrogen metabolism, tumor biology and hyperammonemic diseases. Amino Acids 2015; 48:1-20. [DOI: 10.1007/s00726-015-2061-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 07/24/2015] [Indexed: 12/29/2022]
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10
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Cooper AJL, Kuhara T. α-Ketoglutaramate: an overlooked metabolite of glutamine and a biomarker for hepatic encephalopathy and inborn errors of the urea cycle. Metab Brain Dis 2014; 29:991-1006. [PMID: 24234505 PMCID: PMC4020999 DOI: 10.1007/s11011-013-9444-9] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2013] [Accepted: 10/21/2013] [Indexed: 01/16/2023]
Abstract
Glutamine metabolism is generally regarded as proceeding via glutaminase-catalyzed hydrolysis to glutamate and ammonia, followed by conversion of glutamate to α-ketoglutarate catalyzed by glutamate dehydrogenase or by a glutamate-linked aminotransferase (transaminase). However, another pathway exists for the conversion of glutamine to α-ketoglutarate that is often overlooked, but is widely distributed in nature. This pathway, referred to as the glutaminase II pathway, consists of a glutamine transaminase coupled to ω-amidase. Transamination of glutamine results in formation of the corresponding α-keto acid, namely, α-ketoglutaramate (KGM). KGM is hydrolyzed by ω-amidase to α-ketoglutarate and ammonia. The net glutaminase II reaction is: L - Glutamine + α - keto acid + H2O → α - ketoglutarate + L - amino acid + ammonia. In this mini-review the biochemical importance of the glutaminase II pathway is summarized, with emphasis on the key component KGM. Forty years ago it was noted that the concentration of KGM is increased in the cerebrospinal fluid (CSF) of patients with hepatic encephalopathy (HE) and that the level of KGM in the CSF correlates well with the degree of encephalopathy. In more recent work, we have shown that KGM is markedly elevated in the urine of patients with inborn errors of the urea cycle. It is suggested that KGM may be a useful biomarker for many hyperammonemic diseases including hepatic encephalopathy, inborn errors of the urea cycle, citrin deficiency and lysinuric protein intolerance.
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Affiliation(s)
- Arthur J L Cooper
- Department of Biochemistry and Molecular Biology, New York Medical College, 15 Dana Road, Valhalla, NY, 10595, USA,
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11
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Hettich J, Ryan SD, de Souza ON, Saraiva Macedo Timmers LF, Tsai S, Atai NA, da Hora CC, Zhang X, Kothary R, Snapp E, Ericsson M, Grundmann K, Breakefield XO, Nery FC. Biochemical and cellular analysis of human variants of the DYT1 dystonia protein, TorsinA/TOR1A. Hum Mutat 2014; 35:1101-13. [PMID: 24930953 DOI: 10.1002/humu.22602] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Accepted: 06/04/2014] [Indexed: 12/24/2022]
Abstract
Early-onset dystonia is associated with the deletion of one of a pair of glutamic acid residues (c.904_906delGAG/c.907_909delGAG; p.Glu302del/Glu303del; ΔE 302/303) near the carboxyl-terminus of torsinA, a member of the AAA(+) protein family that localizes to the endoplasmic reticulum lumen and nuclear envelope. This deletion commonly underlies early-onset DYT1 dystonia. While the role of the disease-causing mutation, torsinAΔE, has been established through genetic association studies, it is much less clear whether other rare human variants of torsinA are pathogenic. Two missense variations have been described in single patients: R288Q (c.863G>A; p.Arg288Gln; R288Q) identified in a patient with onset of severe generalized dystonia and myoclonus since infancy and F205I (c.613T>A, p.Phe205Ile; F205I) in a psychiatric patient with late-onset focal dystonia. In this study, we have undertaken a series of analyses comparing the biochemical and cellular effects of these rare variants to torsinAΔE and wild-type (wt) torsinA to reveal whether there are common dysfunctional features. The results revealed that the variants, R288Q and F205I, are more similar in their properties to torsinAΔE protein than to torsinAwt. These findings provide functional evidence for the potential pathogenic nature of these rare sequence variants in the TOR1A gene, thus implicating these pathologies in the development of dystonia.
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Affiliation(s)
- Jasmin Hettich
- Molecular Neurogenetics Unit, Department of Neurology and Center for Molecular Imaging Research, Department of Radiology, Massachusetts General Hospital and Program in Neuroscience, Harvard Medical School, Boston, Massachusetts; Department of Medical Genetics and Applied Genomics, University of Tuebingen, Tübingen, Germany
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Asakura M, Nakano M, Hayashida K, Fujii H, Nakajima M, Atsuda K, Itoh T, Fujiwara R. Human Nitrilase-like Protein Does Not Catalyze the Hydrolysis of Vildagliptin. Drug Metab Pharmacokinet 2014; 29:463-9. [DOI: 10.2133/dmpk.dmpk-14-rg-027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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13
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Weber BW, Kimani SW, Varsani A, Cowan DA, Hunter R, Venter GA, Gumbart JC, Sewell BT. The mechanism of the amidases: mutating the glutamate adjacent to the catalytic triad inactivates the enzyme due to substrate mispositioning. J Biol Chem 2013; 288:28514-23. [PMID: 23946488 DOI: 10.1074/jbc.m113.503284] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
All known nitrilase superfamily amidase and carbamoylase structures have an additional glutamate that is hydrogen bonded to the catalytic lysine in addition to the Glu, Lys, Cys "catalytic triad." In the amidase from Geobacillus pallidus, mutating this glutamate (Glu-142) to a leucine or aspartate renders the enzyme inactive. X-ray crystal structure determination shows that the structural integrity of the enzyme is maintained despite the mutation with the catalytic cysteine (Cys-166), lysine (Lys-134), and glutamate (Glu-59) in positions similar to those of the wild-type enzyme. In the case of the E142L mutant, a chloride ion is located in the position occupied by Glu-142 O(ε1) in the wild-type enzyme and interacts with the active site lysine. In the case of the E142D mutant, this site is occupied by Asp-142 O(δ1.) In neither case is an atom located at the position of Glu-142 O(ε2) in the wild-type enzyme. The active site cysteine of the E142L mutant was found to form a Michael adduct with acrylamide, which is a substrate of the wild-type enzyme, due to an interaction that places the double bond of the acrylamide rather than the amide carbonyl carbon adjacent to the active site cysteine. Our results demonstrate that in the wild-type active site a crucial role is played by the hydrogen bond between Glu-142 O(ε2) and the substrate amino group in positioning the substrate with the correct stereoelectronic alignment to enable the nucleophilic attack on the carbonyl carbon by the catalytic cysteine.
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Affiliation(s)
- Brandon W Weber
- From the Structural Biology Research Unit, Division of Medical Biochemistry, Department of Clinical Laboratory Sciences and
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14
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Liu H, Gao Y, Zhang M, Qiu X, Cooper AJL, Niu L, Teng M. Structures of enzyme-intermediate complexes of yeast Nit2: insights into its catalytic mechanism and different substrate specificity compared with mammalian Nit2. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:1470-81. [PMID: 23897470 DOI: 10.1107/s0907444913009347] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Accepted: 04/06/2013] [Indexed: 11/11/2022]
Abstract
The Nit (nitrilase-like) protein subfamily constitutes branch 10 of the nitrilase superfamily. Nit proteins are widely distributed in nature. Mammals possess two members of the Nit subfamily, namely Nit1 and Nit2. Based on sequence similarity, yeast Nit2 (yNit2) is a homologue of mouse Nit1, a tumour-suppressor protein whose substrate specificity is not yet known. Previous studies have shown that mammalian Nit2 (also a putative tumour suppressor) is identical to ω-amidase, an enzyme that catalyzes the hydrolysis of α-ketoglutaramate (α-KGM) and α-ketosuccinamate (α-KSM) to α-ketoglutarate (α-KG) and oxaloacetate (OA), respectively. In the present study, crystal structures of wild-type (WT) yNit2 and of WT yNit2 in complex with α-KG and with OA were determined. In addition, the crystal structure of the C169S mutant of yNit2 (yNit2-C169S) in complex with an endogenous molecule of unknown structure was also solved. Analysis of the structures revealed that α-KG and OA are covalently bound to Cys169 by the formation of a thioester bond between the sulfhydryl group of the cysteine residue and the γ-carboxyl group of α-KG or the β-carboxyl group of OA, reflecting the presumed reaction intermediates. However, an enzymatic assay suggests that α-KGM is a relatively poor substrate of yNit2. Finally, a ligand was found in the active site of yNit2-C169S that may be a natural substrate of yNit2 or an endogenous regulator of enzyme activity. These crystallographic analyses provide information on the mode of substrate/ligand binding at the active site of yNit2 and insights into the catalytic mechanism. These findings suggest that yNit2 may have broad biological roles in yeast, especially in regard to nitrogen homeostasis, and provide a framework for the elucidation of the substrate specificity and biological role of mammalian Nit1.
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Affiliation(s)
- Hejun Liu
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Science, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
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