1
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Nieto-Domínguez M, Sako A, Enemark-Rasmussen K, Gotfredsen CH, Rago D, Nikel PI. Enzymatic synthesis of mono- and trifluorinated alanine enantiomers expands the scope of fluorine biocatalysis. Commun Chem 2024; 7:104. [PMID: 38724655 PMCID: PMC11082193 DOI: 10.1038/s42004-024-01188-1] [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: 11/28/2023] [Accepted: 04/24/2024] [Indexed: 05/12/2024] Open
Abstract
Fluorinated amino acids serve as an entry point for establishing new-to-Nature chemistries in biological systems, and novel methods are needed for the selective synthesis of these building blocks. In this study, we focused on the enzymatic synthesis of fluorinated alanine enantiomers to expand fluorine biocatalysis. The alanine dehydrogenase from Vibrio proteolyticus and the diaminopimelate dehydrogenase from Symbiobacterium thermophilum were selected for in vitro production of (R)-3-fluoroalanine and (S)-3-fluoroalanine, respectively, using 3-fluoropyruvate as the substrate. Additionally, we discovered that an alanine racemase from Streptomyces lavendulae, originally selected for setting an alternative enzymatic cascade leading to the production of these non-canonical amino acids, had an unprecedented catalytic efficiency in β-elimination of fluorine from the monosubstituted fluoroalanine. The in vitro enzymatic cascade based on the dehydrogenases of V. proteolyticus and S. thermophilum included a cofactor recycling system, whereby a formate dehydrogenase from Pseudomonas sp. 101 (either native or engineered) coupled formate oxidation to NAD(P)H formation. Under these conditions, the reaction yields for (R)-3-fluoroalanine and (S)-3-fluoroalanine reached >85% on the fluorinated substrate and proceeded with complete enantiomeric excess. The selected dehydrogenases also catalyzed the conversion of trifluoropyruvate into trifluorinated alanine as a first-case example of fluorine biocatalysis with amino acids carrying a trifluoromethyl group.
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Affiliation(s)
- Manuel Nieto-Domínguez
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Aboubakar Sako
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | | | | | - Daniela Rago
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Pablo I Nikel
- The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Kongens Lyngby, Denmark.
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2
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Fulton RL, Downs DM. Modulators of a robust and efficient metabolism: Perspective and insights from the Rid superfamily of proteins. Adv Microb Physiol 2023; 83:117-179. [PMID: 37507158 PMCID: PMC10642521 DOI: 10.1016/bs.ampbs.2023.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/30/2023]
Abstract
Metabolism is an integrated network of biochemical pathways that assemble to generate the robust, responsive physiologies of microorganisms. Despite decades of fundamental studies on metabolic processes and pathways, our understanding of the nuance and complexity of metabolism remains incomplete. The ability to predict and model metabolic network structure, and its influence on cellular fitness, is complicated by the persistence of genes of unknown function, even in the best-studied model organisms. This review describes the definition and continuing study of the Rid superfamily of proteins. These studies are presented with a perspective that illustrates how metabolic complexity can complicate the assignment of function to uncharacterized genes. The Rid superfamily of proteins has been divided into eight subfamilies, including the well-studied RidA subfamily. Aside from the RidA proteins, which are present in all domains of life and prevent metabolic stress, most members of the Rid superfamily have no demonstrated physiological role. Recent progress on functional assignment supports the hypothesis that, overall, proteins in the Rid superfamily modulate metabolic processes to ensure optimal organismal fitness.
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Affiliation(s)
- Ronnie L Fulton
- Department of Microbiology, University of Georgia, Athens, GA, United States
| | - Diana M Downs
- Department of Microbiology, University of Georgia, Athens, GA, United States.
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3
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Ghosh RK, Hilario E, Chang CEA, Mueller LJ, Dunn MF. Allosteric regulation of substrate channeling: Salmonella typhimurium tryptophan synthase. Front Mol Biosci 2022; 9:923042. [PMID: 36172042 PMCID: PMC9512447 DOI: 10.3389/fmolb.2022.923042] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Accepted: 08/11/2022] [Indexed: 11/13/2022] Open
Abstract
The regulation of the synthesis of L-tryptophan (L-Trp) in enteric bacteria begins at the level of gene expression where the cellular concentration of L-Trp tightly controls expression of the five enzymes of the Trp operon responsible for the synthesis of L-Trp. Two of these enzymes, trpA and trpB, form an αββα bienzyme complex, designated as tryptophan synthase (TS). TS carries out the last two enzymatic processes comprising the synthesis of L-Trp. The TS α-subunits catalyze the cleavage of 3-indole D-glyceraldehyde 3′-phosphate to indole and D-glyceraldehyde 3-phosphate; the pyridoxal phosphate-requiring β-subunits catalyze a nine-step reaction sequence to replace the L-Ser hydroxyl by indole giving L-Trp and a water molecule. Within αβ dimeric units of the αββα bienzyme complex, the common intermediate indole is channeled from the α site to the β site via an interconnecting 25 Å-long tunnel. The TS system provides an unusual example of allosteric control wherein the structures of the nine different covalent intermediates along the β-reaction catalytic path and substrate binding to the α-site provide the allosteric triggers for switching the αββα system between the open (T) and closed (R) allosteric states. This triggering provides a linkage that couples the allosteric conformational coordinate to the covalent chemical reaction coordinates at the α- and β-sites. This coupling drives the α- and β-sites between T and R conformations to achieve regulation of substrate binding and/or product release, modulation of the α- and β-site catalytic activities, prevention of indole escape from the confines of the active sites and the interconnecting tunnel, and synchronization of the α- and β-site catalytic activities. Here we review recent advances in the understanding of the relationships between structure, function, and allosteric regulation of the complex found in Salmonella typhimurium.
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Affiliation(s)
- Rittik K. Ghosh
- Department of Biochemistry, University of California, Riverside, Riverside, CA, United States
| | - Eduardo Hilario
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
| | - Chia-en A. Chang
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
| | - Leonard J. Mueller
- Department of Chemistry, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Leonard J. Mueller, ; Michael F. Dunn,
| | - Michael F. Dunn
- Department of Biochemistry, University of California, Riverside, Riverside, CA, United States
- *Correspondence: Leonard J. Mueller, ; Michael F. Dunn,
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4
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Ghosh RK, Hilario E, Liu V, Wang Y, Niks D, Holmes JB, Sakhrani VV, Mueller LJ, Dunn MF. Mutation of βGln114 to Ala Alters the Stabilities of Allosteric States in Tryptophan Synthase Catalysis. Biochemistry 2021; 60:3173-3186. [PMID: 34595921 DOI: 10.1021/acs.biochem.1c00383] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The tryptophan synthase (TS) bienzyme complexes found in bacteria, yeasts, and molds are pyridoxal 5'-phosphate (PLP)-requiring enzymes that synthesize l-Trp. In the TS catalytic cycle, switching between the open and closed states of the α- and β-subunits via allosteric interactions is key to the efficient conversion of 3-indole-d-glycerol-3'-phosphate and l-Ser to l-Trp. In this process, the roles played by β-site residues proximal to the PLP cofactor have not yet been fully established. βGln114 is one such residue. To explore the roles played by βQ114, we conducted a detailed investigation of the βQ114A mutation on the structure and function of tryptophan synthase. Initial steady-state kinetic and static ultraviolet-visible spectroscopic analyses showed the Q to A mutation impairs catalytic activity and alters the stabilities of intermediates in the β-reaction. Therefore, we conducted X-ray structural and solid-state nuclear magnetic resonance spectroscopic studies to compare the wild-type and βQ114A mutant enzymes. These comparisons establish that the protein structural changes are limited to the Gln to Ala replacement, the loss of hydrogen bonds among the side chains of βGln114, βAsn145, and βArg148, and the inclusion of waters in the cavity created by substitution of the smaller Ala side chain. Because the conformations of the open and closed allosteric states are not changed by the mutation, we hypothesize that the altered properties arise from the lost hydrogen bonds that alter the relative stabilities of the open (βT state) and closed (βR state) conformations of the β-subunit and consequently alter the distribution of intermediates along the β-subunit catalytic path.
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Affiliation(s)
- Rittik K Ghosh
- Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Eduardo Hilario
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Viktoriia Liu
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Yangyang Wang
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Dimitri Niks
- Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Jacob B Holmes
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Varun V Sakhrani
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Leonard J Mueller
- Department of Chemistry, University of California, Riverside, California 92521, United States
| | - Michael F Dunn
- Department of Biochemistry, University of California, Riverside, California 92521, United States
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5
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Irons JL, Hodge-Hanson K, Downs DM. RidA Proteins Protect against Metabolic Damage by Reactive Intermediates. Microbiol Mol Biol Rev 2020; 84:e00024-20. [PMID: 32669283 PMCID: PMC7373157 DOI: 10.1128/mmbr.00024-20] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The Rid (YjgF/YER057c/UK114) protein superfamily was first defined by sequence homology with available protein sequences from bacteria, archaea, and eukaryotes (L. Parsons, N. Bonander, E. Eisenstein, M. Gilson, et al., Biochemistry 42:80-89, 2003, https://doi.org/10.1021/bi020541w). The archetypal subfamily, RidA (reactive intermediate deaminase A), is found in all domains of life, with the vast majority of free-living organisms carrying at least one RidA homolog. In over 2 decades, close to 100 reports have implicated Rid family members in cellular processes in prokaryotes, yeast, plants, and mammals. Functional roles have been proposed for Rid enzymes in amino acid biosynthesis, plant root development and nutrient acquisition, cellular respiration, and carcinogenesis. Despite the wealth of literature and over a dozen high-resolution structures of different RidA enzymes, their biochemical function remained elusive for decades. The function of the RidA protein was elucidated in a bacterial model system despite (i) a minimal phenotype of ridA mutants, (ii) the enzyme catalyzing a reaction believed to occur spontaneously, and (iii) confusing literature on the pleiotropic effects of RidA homologs in prokaryotes and eukaryotes. Subsequent work provided the physiological framework to support the RidA paradigm in Salmonella enterica by linking the phenotypes of mutants lacking ridA to the accumulation of the reactive metabolite 2-aminoacrylate (2AA), which damaged metabolic enzymes. Conservation of enamine/imine deaminase activity of RidA enzymes from all domains raises the likelihood that, despite the diverse phenotypes, the consequences when RidA is absent are due to accumulated 2AA (or a similar reactive enamine) and the diversity of metabolic phenotypes can be attributed to differences in metabolic network architecture. The discovery of the RidA paradigm in S. enterica laid a foundation for assessing the role of Rid enzymes in diverse organisms and contributed fundamental lessons on metabolic network evolution and diversity in microbes. This review describes the studies that defined the conserved function of RidA, the paradigm of enamine stress in S. enterica, and emerging studies that explore how this paradigm differs in other organisms. We focus primarily on the RidA subfamily, while remarking on our current understanding of the other Rid subfamilies. Finally, we describe the current status of the field and pose questions that will drive future studies on this widely conserved protein family to provide fundamental new metabolic information.
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Affiliation(s)
- Jessica L Irons
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
| | | | - Diana M Downs
- Department of Microbiology, University of Georgia, Athens, Georgia, USA
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6
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Favrot L, Amorim Franco TM, Blanchard JS. Biochemical Characterization of the Mycobacterium smegmatis Threonine Deaminase. Biochemistry 2018; 57:6003-6012. [PMID: 30226377 DOI: 10.1021/acs.biochem.8b00871] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The biosynthesis of branched-chain amino acids or BCAAs (l-isoleucine, l-leucine, and l-valine) is essential in eubacteria, but mammals are branched-chain amino acid auxotrophs, making the enzymes in the pathway excellent targets for antibacterial drug development. The biosynthesis of l-isoleucine, l-leucine, and l-valine is very efficient, requiring only eight enzymes. Threonine dehydratase (TD), a pyridoxal 5'-phosphate (PLP)-dependent enzyme encoded by the ilvA gene, is the enzyme responsible for the conversion of l-threonine (l-Thr) to α-ketobutyrate, ammonia, and water, which is the first step in the biosynthesis of l-isoleucine. We have cloned, expressed, and biochemically characterized the reaction catalyzed by Mycobacterium smegmatis TD (abbreviated as MsIlvA) using steady-state kinetics and kinetic isotope effects. We show here that in addition to l-threonine, l-allo-threonine and l-serine are also used as substrates by TD, and all exhibit sigmoidal, non-Michaelis-Menten kinetics. Curiously, β-chloro-l-alanine was also a substrate rather than an inhibitor as expected. The enzymatic activity of TD is sensitive to the presence of allosteric regulators, including the activator l-valine or the end product feedback inhibitor of the BCAA pathway in which TD is involved, l-isoleucine. Primary deuterium kinetic isotopes are small, suggesting Cα proton abstraction is only partially rate-limiting. Solvent kinetic isotopes were significantly larger, indicating that a proton transfer occurring during the reaction is also partially rate-limiting. Finally, we demonstrate that l-cycloserine, a general inhibitor of PLP-dependent enzymes, is an excellent inhibitor of threonine deaminase.
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Affiliation(s)
- Lorenza Favrot
- Department of Biochemistry , Albert Einstein College of Medicine , 1300 Morris Park Avenue , Bronx , New York 10461 , United States
| | - Tathyana M Amorim Franco
- Department of Biochemistry , Albert Einstein College of Medicine , 1300 Morris Park Avenue , Bronx , New York 10461 , United States
| | - John S Blanchard
- Department of Biochemistry , Albert Einstein College of Medicine , 1300 Morris Park Avenue , Bronx , New York 10461 , United States
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7
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Klika KD, Wzorek A, Soloshonok VA. Internal chirality descriptors iR
and iS
and ire
and isi
. A proposed notation to extend the usefulness of the R
/S
system by retaining the sense of stereochemistry in cases of ligand ranking changes. Chirality 2018; 30:1054-1066. [DOI: 10.1002/chir.22982] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 04/25/2018] [Accepted: 05/09/2018] [Indexed: 11/11/2022]
Affiliation(s)
- Karel D. Klika
- Molecular Structure Analysis; German Cancer Research Center (DKFZ); Heidelberg Germany
| | - Alicja Wzorek
- Institute of Chemistry; Jan Kochanowski University in Kielce; Kielce Poland
| | - Vadim A. Soloshonok
- Department of Organic Chemistry I; University of the Basque Country UPV/EHU; San Sebastián Spain
- IKERBASQUE; Basque Foundation for Science; Bilbao Spain
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8
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Glutamate Racemase Is the Primary Target of β-Chloro-d-Alanine in Mycobacterium tuberculosis. Antimicrob Agents Chemother 2016; 60:6091-9. [PMID: 27480853 PMCID: PMC5038272 DOI: 10.1128/aac.01249-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 07/21/2016] [Indexed: 01/18/2023] Open
Abstract
The increasing global prevalence of drug resistance among many leading human pathogens necessitates both the development of antibiotics with novel mechanisms of action and a better understanding of the physiological activities of preexisting clinically effective drugs. Inhibition of peptidoglycan (PG) biosynthesis and cross-linking has traditionally enjoyed immense success as an antibiotic target in multiple bacterial pathogens, except in Mycobacterium tuberculosis, where it has so far been underexploited. d-Cycloserine, a clinically approved antituberculosis therapeutic, inhibits enzymes within the d-alanine subbranch of the PG-biosynthetic pathway and has been a focus in our laboratory for understanding peptidoglycan biosynthesis inhibition and for drug development in studies of M. tuberculosis. During our studies on alternative inhibitors of the d-alanine pathway, we discovered that the canonical alanine racemase (Alr) inhibitor β-chloro–d-alanine (BCDA) is a very poor inhibitor of recombinant M. tuberculosis Alr, despite having potent antituberculosis activity. Through a combination of enzymology, microbiology, metabolomics, and proteomics, we show here that BCDA does not inhibit the d-alanine pathway in intact cells, consistent with its poor in vitro activity, and that it is instead a mechanism-based inactivator of glutamate racemase (MurI), an upstream enzyme in the same early stage of PG biosynthesis. This is the first report to our knowledge of inhibition of MurI in M. tuberculosis and thus provides a valuable tool for studying this essential and enigmatic enzyme and a starting point for future MurI-targeted antibacterial development.
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9
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Downs DM, Ernst DC. From microbiology to cancer biology: the Rid protein family prevents cellular damage caused by endogenously generated reactive nitrogen species. Mol Microbiol 2015; 96:211-9. [PMID: 25620221 DOI: 10.1111/mmi.12945] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/21/2015] [Indexed: 01/03/2023]
Abstract
The Rid family of proteins is highly conserved and broadly distributed throughout the domains of life. Genetic and biochemical studies, primarily in Salmonella enterica, have defined a role for RidA in responding to endogenously generated reactive metabolites. The data show that 2-aminoacrylate (2AA), a reactive enamine intermediate generated by some pyridoxal 5'-phosphate-dependent enzymes, accumulates in the absence of RidA. The accumulation of 2AA leads to covalent modification and inactivation of several enzymes involved in essential metabolic processes. This review describes the 2AA hydrolyzing activity of RidA and the effect of this biochemical activity on the metabolic network, which impacts organism fitness. The reported activity of RidA and the consequences encountered in vivo when RidA is absent have challenged fundamental assumptions in enzymology, biochemistry and cell metabolism regarding the fate of transiently generated reactive enamine intermediates. The current understanding of RidA in Salmonella and the broad distribution of Rid family proteins provide exciting opportunities for future studies to define metabolic roles of Rid family members from microbes to man.
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Affiliation(s)
- Diana M Downs
- Department of Microbiology, University of Georgia, 120 Cedar Street, Athens, GA, 30602-2605, USA
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10
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Koszelewski D, Zysk M, Brodzka A, Żądło A, Paprocki D, Ostaszewski R. Evaluation of a new protocol for enzymatic dynamic kinetic resolution of 3-hydroxy-3-(aryl)propanoic acids. Org Biomol Chem 2015; 13:11014-20. [DOI: 10.1039/c5ob01380a] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The application of tandem metal–enzyme dynamic kinetic resolution (DKR) is a powerful tool for the manufacture of high-value chemical commodities.
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Affiliation(s)
| | - Małgorzata Zysk
- Institute of Organic Chemistry PAS Kasprzaka 44/52
- 01-224 Warsaw
- Poland
| | - Anna Brodzka
- Institute of Organic Chemistry PAS Kasprzaka 44/52
- 01-224 Warsaw
- Poland
| | - Anna Żądło
- Institute of Organic Chemistry PAS Kasprzaka 44/52
- 01-224 Warsaw
- Poland
| | - Daniel Paprocki
- Institute of Organic Chemistry PAS Kasprzaka 44/52
- 01-224 Warsaw
- Poland
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11
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Alvarez L, Espaillat A, Hermoso JA, de Pedro MA, Cava F. Peptidoglycan remodeling by the coordinated action of multispecific enzymes. Microb Drug Resist 2014; 20:190-8. [PMID: 24799190 DOI: 10.1089/mdr.2014.0047] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The peptidoglycan (PG) cell wall constitutes the main defense barrier of bacteria against environmental insults and acts as communication interface. The biochemistry of this macromolecule has been well characterized throughout the years but recent discoveries have unveiled its chemical plasticity under environmental stresses. Non-canonical D-amino acids (NCDAA) are produced and released to the extracellular media by diverse bacteria. Such molecules govern cell wall adaptation to challenging environments through their incorporation into the polymer, a widespread capability among bacteria that reveals the inherent catalytic plasticity of the enzymes involved in the cell wall metabolism. Here, we analyze the recent structural and biochemical characterization of Bsr, a new family of broad spectrum racemases able to generate a wide range of NCDAA. We also discuss the necessity of a coordinated action of PG multispecific enzymes to generate adequate levels of modification in the murein sacculus. Finally, we also highlight how this catalytic plasticity of NCDAA-incorporating enzymes has allowed the development of new revolutionary methodologies for the study of PG modes of growth and in vivo dynamics.
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Affiliation(s)
- Laura Alvarez
- 1 Laboratory for Molecular Infection Medicine Sweden, Department of Molecular Biology, Umeå Centre for Microbial Research, Umeå University , Umeå, Sweden
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12
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Flynn JM, Downs DM. In the absence of RidA, endogenous 2-aminoacrylate inactivates alanine racemases by modifying the pyridoxal 5'-phosphate cofactor. J Bacteriol 2013; 195:3603-9. [PMID: 23749972 PMCID: PMC3754577 DOI: 10.1128/jb.00463-13] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2013] [Accepted: 05/31/2013] [Indexed: 11/20/2022] Open
Abstract
Members of the RidA (YjgF/YER057c/UK114) protein family are broadly conserved across the domains of life. In vitro, these proteins deaminate 3- or 4-carbon enamines that are generated as mechanistic intermediates of pyridoxal 5'-phosphate (PLP)-dependent serine/threonine dehydratases. The three-carbon enamine 2-aminoacrylate can inactivate some enzymes by forming a covalent adduct via a mechanism that has been well characterized in vitro. The biochemical activity of RidA suggested that the phenotypes of ridA mutant strains were caused by the accumulation of reactive enamine metabolites. The data herein show that in ridA mutant strains of Salmonella enterica, a stable 2-aminoacrylate (2-AA)/PLP adduct forms on the biosynthetic alanine racemase, Alr, indicating the presence of 2-aminoacrylate in vivo. This study confirms the deleterious effect of 2-aminoacrylate generated by metabolic enzymes and emphasizes the need for RidA to quench this reactive metabolite.
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Affiliation(s)
- Jeffrey M. Flynn
- Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin, USA
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13
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Lambrecht JA, Schmitz GE, Downs DM. RidA proteins prevent metabolic damage inflicted by PLP-dependent dehydratases in all domains of life. mBio 2013; 4:e00033-13. [PMID: 23386433 PMCID: PMC3565831 DOI: 10.1128/mbio.00033-13] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2013] [Accepted: 01/15/2013] [Indexed: 11/30/2022] Open
Abstract
Pyridoxal 5'-phosphate (PLP) is a coenzyme synthesized by all forms of life. Relevant to the work reported here is the mechanism of the PLP-dependent threonine/serine dehydratases, which generate reactive enamine/imine intermediates that are converted to keto acids by members of the RidA family of enzymes. The RidA protein of Salmonella enterica serovar Typhimurium LT2 is the founding member of this broadly conserved family of proteins (formerly known as YjgF/YER057c/UK114). RidA proteins were recently shown to be enamine deaminases. Here we demonstrate the damaging potential of enamines in the absence of RidA proteins. Notably, S. enterica strains lacking RidA have decreased activity of the PLP-dependent transaminase B enzyme IlvE, an enzyme involved in branched-chain amino acid biosynthesis. We reconstituted the threonine/serine dehydratase (IlvA)-dependent inhibition of IlvE in vitro, show that the in vitro system reflects the mechanism of RidA function in vivo, and show that IlvE inhibition is prevented by RidA proteins from all domains of life. We conclude that 2-aminoacrylate (2AA) inhibition represents a new type of metabolic damage, and this finding provides an important physiological context for the role of the ubiquitous RidA family of enamine deaminases in preventing damage by 2AA. IMPORTANCE External stresses that disrupt metabolic components can perturb cellular functions and affect growth. A similar consequence is expected if endogenously generated metabolites are reactive and persist in the cellular environment. Here we show that the metabolic intermediate 2-aminoacrylate (2AA) causes significant cellular damage if allowed to accumulate aberrantly. Furthermore, we show that the widely conserved protein RidA prevents this accumulation by facilitating conversion of 2AA to a stable metabolite. This work demonstrates that the reactive metabolite 2AA, previously considered innocuous in the cell due to a short half-life in aqueous solution, can survive in the cellular environment long enough to cause damage. This work provides insights into the roles and persistence of reactive metabolites in vivo and shows that the RidA family of proteins is able to prevent damage caused by a reactive intermediate that is created as a consequence of PLP-dependent chemistry.
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14
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Griswold WR, Toney MD. Role of the pyridine nitrogen in pyridoxal 5'-phosphate catalysis: activity of three classes of PLP enzymes reconstituted with deazapyridoxal 5'-phosphate. J Am Chem Soc 2011; 133:14823-30. [PMID: 21827189 DOI: 10.1021/ja2061006] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Pyridoxal 5'-phosphate (PLP; vitamin B(6))-catalyzed reactions have been well studied, both on enzymes and in solution, due to the variety of important reactions this cofactor catalyzes in nitrogen metabolism. Three functional groups are central to PLP catalysis: the C4' aldehyde, the O3' phenol, and the N1 pyridine nitrogen. In the literature, the pyridine nitrogen has traditionally been assumed to be protonated in enzyme active sites, with the protonated pyridine ring providing resonance stabilization of carbanionic intermediates. This assumption is certainly correct for some PLP enzymes, but the structures of other active sites are incompatible with protonation of N1, and, consequently, these enzymes are expected to use PLP in the N1-unprotonated form. For example, aspartate aminotransferase protonates the pyridine nitrogen for catalysis of transamination, while both alanine racemase and O-acetylserine sulfhydrylase are expected to maintain N1 in the unprotonated, formally neutral state for catalysis of racemization and β-elimination. Herein, kinetic results for these three enzymes reconstituted with 1-deazapyridoxal 5'-phosphate, an isosteric analogue of PLP lacking the pyridine nitrogen, are compared to those for the PLP enzyme forms. They demonstrate that the pyridine nitrogen is vital to the 1,3-prototropic shift central to transamination, but not to reactions catalyzed by alanine racemase or O-acetylserine sulfhydrylase. Not all PLP enzymes require the electrophilicity of a protonated pyridine ring to enable formation of carbanionic intermediates. It is proposed that modulation of cofactor electrophilicity plays a central role in controlling reaction specificity in PLP enzymes.
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Affiliation(s)
- Wait R Griswold
- Department of Chemistry, University of California, One Shields Avenue, Davis, California 95616, USA
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15
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Lin YL, Gao J, Rubinstein A, Major DT. Molecular dynamics simulations of the intramolecular proton transfer and carbanion stabilization in the pyridoxal 5'-phosphate dependent enzymes L-dopa decarboxylase and alanine racemase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1438-46. [PMID: 21600315 DOI: 10.1016/j.bbapap.2011.05.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2011] [Revised: 04/28/2011] [Accepted: 05/03/2011] [Indexed: 10/18/2022]
Abstract
Molecular dynamics simulations using a combined quantum mechanical and molecular mechanical (QM/MM) potential have been carried out to investigate the internal proton transfer equilibrium of the external aldimine species in l-dopa decarboxylase, and carbanion stabilization by the enzyme cofactor in the active site of alanine racemase. Solvent effects lower the free energy of the O-protonated PLP tautomer both in aqueous solution and in the active site, resulting a free energy difference of about -1 kcal/mol relative to the N-protonated Schiff base in the enzyme. The external aldimine provides the dominant contribution to lowering the free energy barrier for the spontaneous decarboxylation of l-dopa in water, by a remarkable 16 kcal/mol, while the enzyme l-dopa decarboxylase further lowers the barrier by 8 kcal/mol. Kinetic isotope effects were also determined using a path integral free energy perturbation theory on the primary (13)C and the secondary (2)H substitutions. In the case of alanine racemase, if the pyridine ring is unprotonated as that in the active site, there is destabilizing contribution to the formation of the α-carbanion in the gas phase, although when the pyridine ring is protonated the contribution is stabilizing. In aqueous solution and in alanine racemase, the α-carbanion is stabilized both when the pyridine ring is protonated and unprotonated. The computational studies illustrated in this article show that combined QM/MM simulations can help provide a deeper understanding of the mechanisms of PLP-dependent enzymes. This article is part of a Special Issue entitled: Pyridoxal Phosphate Enzymology.
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Affiliation(s)
- Yen-Lin Lin
- Department of Chemistry, Digital Technology Center and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455, USA
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16
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van Genderen MHP, Buck HM. The role of axial chirality in schiff bases of pyridoxal phosphate and amino acids in the mechanism of racemase enzymes. A quantum-chemical study. ACTA ACUST UNITED AC 2010. [DOI: 10.1002/recl.19891081105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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17
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Rubinstein A, Major DT. Understanding Catalytic Specificity in Alanine Racemase from Quantum Mechanical and Molecular Mechanical Simulations of the Arginine 219 Mutant. Biochemistry 2010; 49:3957-64. [DOI: 10.1021/bi1002629] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Amir Rubinstein
- Department of Chemistry and Lise Meitner-Minerva Center of Computational Quantum Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
| | - Dan Thomas Major
- Department of Chemistry and Lise Meitner-Minerva Center of Computational Quantum Chemistry, Bar-Ilan University, Ramat-Gan 52900, Israel
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Matsui D, Oikawa T, Arakawa N, Osumi S, Lausberg F, Stäbler N, Freudl R, Eggeling L. A periplasmic, pyridoxal-5'-phosphate-dependent amino acid racemase in Pseudomonas taetrolens. Appl Microbiol Biotechnol 2009; 83:1045-54. [PMID: 19300994 DOI: 10.1007/s00253-009-1942-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2009] [Revised: 03/03/2009] [Accepted: 03/03/2009] [Indexed: 11/26/2022]
Abstract
The pyridoxal-5'-phosphate (PLP)-dependent amino acid racemases occur in almost every bacterium but may differ considerably with respect to substrate specificity. We here isolated the cloned broad substrate specificity racemase ArgR of Pseudomonas taetrolens from Escherichia coli by classical procedures. The racemase was biochemically characterized and amongst other aspects it was confirmed that it is mostly active with lysine, arginine and ornithine, but merely weakly active with alanine, whereas the alanine racemase of the same organism studied in comparison acts on alanine only. Unexpectedly, sequencing the amino-terminal end of ArgR revealed processing of the protein, with a signal peptide cleaved off. Subsequent localization studies demonstrated that in both P. taetrolens and E. coli ArgR activity was almost exclusively present in the periplasm, a feature so far unknown for any amino acid racemase. An ArgR-derivative carrying a carboxy-terminal His-tag was made and this was demonstrated to localize even in an E. coli mutant devoid of the twin-arginine translocation (Tat) pathway in the periplasm. These data indicate that ArgR is synthesized as a prepeptide and translocated in a Tat-independent manner. We therefore propose that ArgR translocation depends on the Sec system and a post-translocational insertion of PLP occurs. As further experiments showed, ArgR is necessary for the catabolism of D: -arginine and D: -lysine by P. taetrolens.
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Affiliation(s)
- Daisuke Matsui
- Department of Life Science and Biotechnology, Kansai University, Yamate-Cho, Suita, Osaka-Fu, Japan
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19
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Yamauchi T, Goto M, Wu HY, Uo T, Yoshimura T, Mihara H, Kurihara T, Miyahara I, Hirotsu K, Esaki N. Serine Racemase with Catalytically Active Lysinoalanyl Residue*. ACTA ACUST UNITED AC 2009; 145:421-4. [DOI: 10.1093/jb/mvp010] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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20
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Kino K, Sato M, Yoneyama M, Kirimura K. Synthesis of dl-tryptophan by modified broad specificity amino acid racemase from Pseudomonas putida IFO 12996. Appl Microbiol Biotechnol 2007; 73:1299-305. [PMID: 17028872 DOI: 10.1007/s00253-006-0600-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2006] [Revised: 07/30/2006] [Accepted: 08/07/2006] [Indexed: 12/24/2022]
Abstract
Broad specificity amino acid racemase (E.C. 5.1.1.10) from Pseudomonas putida IFO 12996 (BAR) is a unique racemase because of its broad substrate specificity. BAR has been considered as a possible catalyst which directly converts inexpensive L-amino acids to DL-amino acid racemates. The gene encoding BAR was cloned to utilize BAR for the synthesis of D-amino acids, especially D-Trp which is an important intermediate of pharmaceuticals. The substrate specificity of cloned BAR covered all of the standard amino acids; however, the activity toward Trp was low. Then, we performed random mutagenesis on bar to obtain mutant BAR derivatives with high activity for Trp. Five positive mutants were isolated after the two-step screening of the randomly mutated BAR. After the determination of the amino acid substitutions in these mutants, it was suggested that the substitutions at Y396 and I384 increased the Trp specific racemization activity and the racemization activity for overall amino acids, respectively. Among the positive mutants, I384M mutant BAR showed the highest activity for Trp. L-Trp (20 mM) was successfully racemized, and the proportion of D-Trp was reached 43% using I384M mutant BAR, while wild-type BAR racemized only 6% of initial L-Trp.
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Affiliation(s)
- Kuniki Kino
- Laboratory of Applied Biochemistry, Department of Applied Chemistry, School of Science and Engineering,Waseda University, 3-4-1 Okubo, Shinjuku-ku, 169-8555, Tokyo, Japan.
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21
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Shibata K, Watanabe T, Yoshikawa H, Abe K, Takahashi S, Kera Y, Yamada RH. Purification and characterization of aspartate racemase from the bivalve mollusk Scapharca broughtonii. Comp Biochem Physiol B Biochem Mol Biol 2003; 134:307-14. [PMID: 12568809 DOI: 10.1016/s1096-4959(02)00267-1] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High concentrations of D-aspartate occur in blood shell Scapharca broughtonii (Mollusca) tissues. We purified aspartate racemase from the foot muscle of the bivalve to electrophoretic homogeneity. The molecular mass shown by sodium dodecyl sulfate polyacrylamide gel was 39 kDa, while that shown by gel filtration ranged from 51 to 63 kDa. Pyridoxal 5'-phosphate-dependency of the enzyme was demonstrated by its absorption spectrum as well as the effects of amino-oxyacetate and other reagents on the activity and spectrum. The enzyme is highly specific to aspartate and does not racemize L-alanine, L-serine and L-glutamate. It showed the highest activity at pH 8 both in the conversion of L- to D- and D- to L-aspartate, and the optimal temperature was 25 degrees C. V(max) and K(m) values for L-aspartate were 7.39 micromolmin(-1)mg(-1) and 60.4 mM and those for D-aspartate were 22.6 micromolmin(-1)mg(-1) and 159 mM, respectively.
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Affiliation(s)
- Kimihiko Shibata
- Department of Environmental Systems Engineering, Nagaoka University of Technology, Nagaoka, Niigata 940-2188, Japan
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22
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23
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Nomura T, Yamamoto I, Morishita F, Furukawa Y, Matsushima O. Purification and some properties of alanine racemase from a bivalve mollusc Corbicula japonica. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 2001; 289:1-9. [PMID: 11169488 DOI: 10.1002/1097-010x(20010101/31)289:1<1::aid-jez1>3.0.co;2-m] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A brackish-water mollusc, Corbicula japonica, uses large quantities of D- and L-alanine as intracellular osmotically active solutes, osmolytes, for regulation of intracellular osmolarity. We purified alanine racemase from the mantle of C. japonica to characterize its enzymological properties. The molecular masses of the enzyme were estimated to be 41 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 140 kDa by gel filtration on high-performance liquid chromatography, suggesting the trimeric or tetrameric nature of the enzyme. Neither dialysis nor chromatographic procedures in the absence of pyridoxal 5'-phosphate led to loss of enzyme activity, although carbonyl reagents, hydroxylamine and phenylhydrazine, inhibited the activity. These results suggest that alanine racemase of the animal may bind pyridoxal 5'-phosphate tightly as a cofactor. Kinetic experiments using the partially purified enzyme revealed that alanine was the sole substrate among 17 kinds of L-amino acids tested. The Lineweaver-Burk plot for L-alanine as substrate resulted in Km value of 22.6 mM, and the value for D-alanine was 9.2 mM. Together with the previous evidence that D- and L-alanine levels of this animal change with the external salinity maintaining the D-/L-alanine ratio at unity, the present results seem to indicate that the physiological role of alanine racemase in this animal is to supply D-alanine as a main intracellular osmolyte. J. Exp. Zool. 289:1-9, 2001.
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Affiliation(s)
- T Nomura
- Department of Biological Science, Faculty of Science, Hiroshima University, Kagamiyama, Higashi Hiroshima 739-8526, Japan
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24
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Mihara H, Kurihara T, Yoshimura T, Soda K, Esaki N. Cysteine sulfinate desulfinase, a NIFS-like protein of Escherichia coli with selenocysteine lyase and cysteine desulfurase activities. Gene cloning, purification, and characterization of a novel pyridoxal enzyme. J Biol Chem 1997; 272:22417-24. [PMID: 9278392 DOI: 10.1074/jbc.272.36.22417] [Citation(s) in RCA: 125] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Selenocysteine lyase (EC 4.4.1.16) exclusively decomposes selenocysteine to alanine and elemental selenium, whereas cysteine desulfurase (NIFS protein) of Azotobacter vinelandii acts indiscriminately on both cysteine and selenocysteine to produce elemental sulfur and selenium respectively, and alanine. These proteins exhibit some sequence homology. The Escherichia coli genome contains three genes with sequence homology to nifS. We have cloned the gene mapped at 63.4 min in the chromosome and have expressed, purified to homogeneity, and characterized the gene product. The enzyme comprises two identical subunits with 401 amino acid residues (Mr 43,238) and contains pyridoxal 5'-phosphate as a coenzyme. The enzyme catalyzes the removal of elemental sulfur and selenium atoms from L-cysteine, L-cystine, L-selenocysteine, and L-selenocystine to produce L-alanine. Because L-cysteine sulfinic acid was desulfinated to form L-alanine as the preferred substrate, we have named this new enzyme cysteine sulfinate desulfinase. Mutant enzymes having alanine substituted for each of the four cysteinyl residues (Cys-100, Cys-176, Cys-323, and Cys-358) were all active. Cys-358 corresponds to Cys-325 of A. vinelandii NIFS, which is conserved among all NIFS-like proteins and catalytically essential (Zheng, L., White, R. H., Cash, V. L., and Dean, D. R. (1994) Biochemistry 33, 4714-4720), is not required for cysteine sulfinate desulfinase. Thus, the enzyme is distinct from A. vinelandii NIFS in this respect.
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Affiliation(s)
- H Mihara
- Laboratory of Microbial Biochemistry, Institute for Chemical Research, Kyoto University, Uji, Kyoto 611, Japan
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25
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Cáceres NE, Harris NB, Wellehan JF, Feng Z, Kapur V, Barletta RG. Overexpression of the D-alanine racemase gene confers resistance to D-cycloserine in Mycobacterium smegmatis. J Bacteriol 1997; 179:5046-55. [PMID: 9260945 PMCID: PMC179361 DOI: 10.1128/jb.179.16.5046-5055.1997] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
D-Cycloserine is an effective second-line drug against Mycobacterium avium and Mycobacterium tuberculosis. To analyze the genetic determinants of D-cycloserine resistance in mycobacteria, a library of a resistant Mycobacterium smegmatis mutant was constructed. A resistant clone harboring a recombinant plasmid with a 3.1-kb insert that contained the glutamate decarboxylase (gadA) and D-alanine racemase (alrA) genes was identified. Subcloning experiments demonstrated that alrA was necessary and sufficient to confer a D-cycloserine resistance phenotype. The D-alanine racemase activities of wild-type and recombinant M. smegmatis strains were inhibited by D-cycloserine in a concentration-dependent manner. The D-cycloserine resistance phenotype in the recombinant clone was due to the overexpression of the wild-type alrA gene in a multicopy vector. Analysis of a spontaneous resistant mutant also demonstrated overproduction of wild-type AlrA enzyme. Nucleotide sequence analysis of the overproducing mutant revealed a single transversion (G-->T) at the alrA promoter, which resulted in elevated beta-galactosidase reporter gene expression. Furthermore, transformants of Mycobacterium intracellulare and Mycobacterium bovis BCG carrying the M. smegmatis wild-type alrA gene in a multicopy vector were resistant to D-cycloserine, suggesting that AlrA overproduction is a potential mechanism of D-cycloserine resistance in clinical isolates of M. tuberculosis and other pathogenic mycobacteria. In conclusion, these results show that one of the mechanisms of D-cycloserine resistance in M. smegmatis involves the overexpression of the alrA gene due to a promoter-up mutation.
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Affiliation(s)
- N E Cáceres
- Department of Veterinary and Biomedical Sciences, University of Nebraska, Lincoln 68583-0905, USA
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26
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Ebbers EJ, Ariaans GJ, Houbiers JP, Bruggink A, Zwanenburg B. Controlled racemization of optically active organic compounds: Prospects for asymmetric transformation. Tetrahedron 1997. [DOI: 10.1016/s0040-4020(97)00324-4] [Citation(s) in RCA: 208] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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27
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Hoffmann K, Schneider-Scherzer E, Kleinkauf H, Zocher R. Purification and characterization of eucaryotic alanine racemase acting as key enzyme in cyclosporin biosynthesis. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)99934-5] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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28
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Axelsson BS, Floss HG, Lee S, Saeed A, Spencer PA, Young DW. Stereochemistry of conversion of the suicide substrates β-chloro-D-alanine-andD- andL-serine O-sulfates into pyruvate byD-amino acid aminotransferase and byL-aspartate aminotransferase. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/p19940002137] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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29
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Hopkins MH, Silverman RB. α-Amino acid analogues as mechanism-based inactivators of γ-aminobutyric acid aminotransferase. Bioorg Med Chem Lett 1992. [DOI: 10.1016/s0960-894x(00)80515-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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30
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Mechanism of mutual activation of the tryptophan synthase alpha and beta subunits. Analysis of the reaction specificity and substrate-induced inactivation of active site and tunnel mutants of the beta subunit. J Biol Chem 1991. [DOI: 10.1016/s0021-9258(18)54673-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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31
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Zboińska E, Sztajer H, Lejczak B, Kafarski P. Antibacterial activity of phosphono dipeptides based on 1-amino-1-methylethanephosphonic acid. FEMS Microbiol Lett 1990; 58:23-8. [PMID: 2204574 DOI: 10.1111/j.1574-6968.1990.tb03770.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Phosphono dipeptides containing 1-amino-1-methylethanephosphonic acid (phosphonic acid analogue of alpha-methylalanine, MeAlaP) and glycine, alanine, valine, leucine phenylalanine, proline, methionine or lysine as N- terminal component were synthesized in order to determine their antibacterial properties. Peptides containing alanine, leucine, valine phenylalanine and methionine showed marked in vitro activity, especially against Escherichia coli and Serratia marcescens strains. There were, however, generally less potent than the respective phosphono dipeptides based on 1-aminoethanephosphonic acid (phosphonic acid analogue of alanine, AlaP). The possible mechanism of action of the peptides of MeAlaP involves their active transport into the bacterial cell, followed by intracellular release of MeAlaP, which most likely inhibits alanine racemase, a key enzyme in peptidoglycan biosynthesis. Studies on the uptake of AlaMeAlaP and LeuMeAlaP by Escherichia coli mutants defective in the oligopeptide permease suggest that these peptides are not transported by the oligopeptide transport system.
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Affiliation(s)
- E Zboińska
- Institute of Organic and Physical Chemistry, Technical University of Wrocław, Poland
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32
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Mullins LS, Zawadzke LE, Walsh CT, Raushel FM. Kinetic evidence for the formation of D-alanyl phosphate in the mechanism of D-alanyl-D-alanine ligase. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)38801-5] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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33
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Abstract
The gene encoding thermostable alanine recemase from Bacillus stearothermophilus was cloned and expressed in E. coli. The enzyme was purified to homogeneity from cell extracts of E. coli carrying a plasmid designated pICR4. The alanine racemase gene sequenced was found to contain an open reading frame of 1158 nucleotides. The molecular weight of the enzyme subunit was estimated to be 43,341. The alpha-helical and beta-structure contents were calculated to be about 34 and 26%, respectively, from CD data. CD measurements of the denaturation process of enzyme by guanidine hydrochloride showed the presence of a stable intermediate during the denaturation. Limited proteolysis with subtilisin resulted in the formation of two dissimilar peptide fragments with molecular weights of about 28,000 and 13,000 in the early stage of the digestion. These suggest that the enzyme subunit is composed of two structurally dissimilar domains connected by a short polypeptide (residues 258-266), which first suffers the limited proteolysis. However, the enzyme retained almost full activity and the conformation indistinguishable from the intact protein even when it was proteolytically hydrolyzed to more than 10 fragments.
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Affiliation(s)
- K Soda
- Institute for Chemical Research, Kyoto University, Japan
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34
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Bhattacharjee MK, Snell EE. Pyridoxal 5'-phosphate-dependent histidine decarboxylase. Mechanism of inactivation by alpha-fluoromethylhistidine. J Biol Chem 1990. [DOI: 10.1016/s0021-9258(19)39201-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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35
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Duncan K, Faraci WS, Matteson DS, Walsh CT. (1-Aminoethyl)boronic acid: a novel inhibitor for Bacillus stearothermophilus alanine racemase and Salmonella typhimurium D-alanine:D-alanine ligase (ADP-forming). Biochemistry 1989; 28:3541-9. [PMID: 2663072 DOI: 10.1021/bi00434a059] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
(1-Aminoethyl)boronic acid (Ala-B), an analogue of alanine in which a boronic acid group replaces the carboxyl group, has been synthesized and found to inhibit the first two enzymes, alanine racemase (from Bacillus stearothermophilus, EC 5.1.1.1) and D-alanine:D-alanine ligase (ADP-forming) (from Salmonella typhimurium, EC 6.3.2.4), of the D-alanine branch of bacterial peptidoglycan biosynthesis. In both cases, time-dependent, slow binding inhibition is observed due to the generation of long-lived, slowly dissociating complexes. Ala-B inhibits alanine racemase with a Ki of 20 mM and a kappa inact of 0.15-0.35 min-1. Time-dependent loss of activity is paralleled by conversion of the 420-nm chromophore of initial bound PLP aldimine to a 324-nm absorbing species. On dilution of Ala-B, racemase activity is regained with a t1/2 of ca. 1 h. The D-Ala-D-Ala ligase also shows progressive inhibition by Ala-B provided ATP (but not AMP-PNP or AMP-PCP) is present. The presence of D-alanine along with ATP also leads to Ala-B-induced inactivation. Kinetic analysis suggests Ala-B can compete with D-alanine at either of the two D-alanine binding sites, and on inactivation with Ala-B, labeled D-alanine, and labeled ATP, the inactive enzyme has stoichiometric amounts of D-alanine, ADP, Pi, and Ala-B bound. The half-life of inactive enzyme complexes varied from approximately 2 h (without D-alanine) to 4.5 days (with D-alanine). No D-Ala-D-Ala-B dipeptide was detected.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- K Duncan
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
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36
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SODA KENJI, TANAKA HIDEHIKO, TANIZAWA KATSUYUKI. Thermostable Alanine Racemase and Its Application to D-Amino Acid Synthesis. Ann N Y Acad Sci 1988. [DOI: 10.1111/j.1749-6632.1988.tb25860.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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37
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Silverman RB, George C. Inactivation of gamma-aminobutyric acid aminotransferase by (Z)-4-amino-2-fluorobut-2-enoic acid. Biochemistry 1988; 27:3285-9. [PMID: 3390432 DOI: 10.1021/bi00409a024] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
(Z)-4-Amino-2-fluorobut-2-enoic acid (1) is shown to be a mechanism-based inactivator of pig brain gamma-aminobutyric acid aminotransferase. Approximately 750 inactivator molecules are consumed prior to complete enzyme inactivation. Concurrent with enzyme inactivation is the release of 708 +/- 79 fluoride ions; transamination occurs 737 +/- 15 times per inactivation event. Inactivation of [3H]pyridoxal 5'-phosphate ([3H]PLP) reconstituted GABA aminotransferase by 1 followed by denaturation releases [3H]PMP with no radioactivity remaining attached to the protein. A similar experiment carried out with 4-amino-5-fluoropent-2-enoic acid [Silverman, R. B., Invergo, B. J., & Mathew, J. (1986) J. Med. Chem. 29, 1840-1846] as the inactivator produces no [3H]PMP; rather, another radioactive species is released. These results support an inactivation mechanism for 1 that involves normal catalytic isomerization followed by active site nucleophilic attack on the activated Michael acceptor. A general hypothesis for predicting the inactivation mechanism (Michael addition vs enamine addition) of GABA aminotransferase inactivators is proposed.
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Affiliation(s)
- R B Silverman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208
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38
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Faraci WS, Walsh CT. Racemization of alanine by the alanine racemases from Salmonella typhimurium and Bacillus stearothermophilus: energetic reaction profiles. Biochemistry 1988; 27:3267-76. [PMID: 3291946 DOI: 10.1021/bi00409a022] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Alanine racemases are bacterial pyridoxal 5'-phosphate (PLP) dependent enzymes providing D-alanine as an essential building block for biosynthesis of the peptidoglycan layer of the cell wall. Two isozymic alanine racemases, encoded by the dadB gene and the alr gene, from the Gram-negative mesophilic Salmonella typhimurium and one from the Gram-positive thermophilic Bacillus stearothermophilus have been examined for the racemization mechanism. Substrate deuterium isotope effects and solvent deuterium isotope effects have been measured in both L----D and D----L directions for all three enzymes to assess the degree to which abstraction of the alpha-proton or protonation of substrate PLP carbanion is limiting in catalysis. Additionally, experiments measuring internal return of alpha-3H from substrate to product and solvent exchange/substrate conversion experiments in 3H2O have been used with each enzyme to examine the partitioning of substrate PLP carbanion intermediates and to obtain the relative heights of kinetically significant energy barriers in alanine racemase catalysis.
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Affiliation(s)
- W S Faraci
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139
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Nagasawa T, Tanizawa K, Satoda T, Yamada H. Diaminopropionate ammonia-lyase from Salmonella typhimurium. Purification and characterization of the crystalline enzyme, and sequence determination of the pyridoxal 5'-phosphate binding peptide. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)35446-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Abstract
The copper-containing monooxygenase dopamine beta-hydroxylase catalyzes the hydroxylation of dopamine at the benzylic position to form norepinephrine. Mechanism-based inhibitors for dopamine beta-hydroxylase have been used as probes of the mechanism of catalysis. The variety of such inhibitors that have been developed for this enzyme can be divided into three groups: (i) those in which the inactivating species is formed by abstraction of a hydrogen atom to form a radical intermediate; (ii) those in which the inactivating species is formed by abstraction of an electron to form an epoxide-like intermediate; and (iii) those in which the product is the inactivating species. A mechanism consistent with inactivation by all three groups of inhibitors which proposes that hydroxylation of dopamine by dopamine beta-hydroxylase involves formation of a benzylic radical has been developed. The benzylic radical is formed by abstraction of a hydrogen atom from the substrate by a high-potential copper-oxygen species.
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Affiliation(s)
- P F Fitzpatrick
- Department of Biochemistry and Biophysics, Texas A&M University, College Station
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Silverman RB, Invergo BJ. Mechanism of inactivation of gamma-aminobutyrate aminotransferase by 4-amino-5-fluoropentanoic acid. First example of an enamine mechanism for a gamma-amino acid with a partition ratio of 0. Biochemistry 1986; 25:6817-20. [PMID: 3801394 DOI: 10.1021/bi00370a013] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The mechanism of inactivation of pig brain gamma-aminobutyric acid aminotransferase (GABA-T) by (S)-4-amino-5-fluoropentanoic acid (1, R = CH2CH2COOH, X = F) previously proposed [Silverman, R. B., & Levy, M. A. (1981) Biochemistry 20, 1197-1203] is revised. apo-GABA-T is reconstituted with [4-3H]pyridoxal 5'-phosphate and inactivated with 1 (R = CH2CH2COOH, X = F). Treatment of inactivated enzyme with base followed by acid denaturation leads to the complete release of radioactivity as 6-[2-hydroxy-3-methyl-6-(phosphonoxymethyl)-4-pyridinyl]-4-oxo-5-+ ++hexenoic acid (4, R = CH2CH2COOH). Alkaline phosphatase treatment of this compound produces dephosphorylated 4 (R = CH2CH2COOH). These results support a mechanism that was suggested by Metzler and co-workers [Likos, J. J., Ueno, H., Feldhaus, R. W., & Metzler, D. E. (1982) Biochemistry 21, 4377-4386] for the inactivation of glutamate decarboxylase by serine O-sulfate (Scheme I, pathway b, R = COOH, X = OSO3-).
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Analogs of diaminopimelic acid as inhibitors of meso-diaminopimelate decarboxylase from Bacillus sphaericus and wheat germ. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)69293-2] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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Hayashi H, Tanase S, Snell EE. Pyridoxal 5'-phosphate-dependent histidine decarboxylase. Inactivation by alpha-fluoromethylhistidine and comparative sequences at the inhibitor- and coenzyme-binding sites. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(18)67339-9] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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Boisvert W, Cheung KS, Lerner SA, Johnston M. Mechanisms of action of chloroalanyl antibacterial peptides. Identification of the intracellular enzymes inactivated on treatment of Escherichia coli JSR-O with the dipeptide beta Cl-LAla-beta Cl-LAla. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)57484-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Mobashery S, Johnston M. Reactions of Escherichia coli TEM beta-lactamase with cephalothin and with C10-dipeptidyl cephalosporin esters. J Biol Chem 1986. [DOI: 10.1016/s0021-9258(19)57485-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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47
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McDonald IA, Lacoste JM, Bey P, Wagner J, Zreika M, Palfreyman MG. Dual enzyme-activated irreversible inhibition of monoamine oxidase. Bioorg Chem 1986. [DOI: 10.1016/0045-2068(86)90021-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Badet B, Walsh C. Purification of an alanine racemase from Streptococcus faecalis and analysis of its inactivation by (1-aminoethyl)phosphonic acid enantiomers. Biochemistry 1985; 24:1333-41. [PMID: 3921052 DOI: 10.1021/bi00327a010] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
An alanine racemase has been purified some 30 000-fold almost to homogeneity from Gram-positive Streptococcus faecalis NCIB 6459; the enzyme has been purified to the same extent (4000-fold) from an O-carbamyl-D-serine-resistant mutant with a 7-fold higher enzyme level in crude extract. The racemase has one pyridoxal phosphate molecule per 42-kDa subunit, has a Vmax of 3570 units/mg and a Km of 7.8 mM in the L to D direction, and has a Vmax of 1210 units/mg and a Km of 2.2 mM in the D to L direction. The Keq is 0.8 and kcat/Km values are ca. 3 X 10(5) M-1 s-1. The purified enzyme is inhibited in a time-dependent manner by both L- and D-(l-aminoethyl)phosphonates (Ala-P), confirming observations of Atherton et al. in crude extracts of this organism [Atherton, F. R., Hall, M. J., Hassal, C. H., Holmes, S. W., Lambert, R. W., Lloyd, W. J., & Ringrose, P. S. (1980) Antimicrob. Agents Chemother. 18, 897]. Studies with [1-2H]-, [1-3H]-, and [1,2-14C]Ala-P rule out enzymic activation and processing as the basis for irreversible inhibition. Thus, enzyme after exposure to [14C]Ala-P or [alpha-3H]Ala-P and gel filtration contains stoichiometric amounts of radioactive label, but denaturation quantitatively releases intact Ala-P into solution as revealed by high-performance liquid chromatography and cocrystallization with authentic material. The Ala-P isomers are slow binding inhibitors of this racemase as is the alpha,alpha'-dimethyl analogue but not the D or L isomers of the corresponding phosphinate.(ABSTRACT TRUNCATED AT 250 WORDS)
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