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Mechanisms of Acetoin Toxicity and Adaptive Responses in an Acetoin-Producing Species, Lactococcus lactis. Appl Environ Microbiol 2021; 87:e0107921. [PMID: 34613757 PMCID: PMC8612267 DOI: 10.1128/aem.01079-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Acetoin, 3-hydroxyl,2-butanone, is extensively used as a flavor additive in food products. This volatile compound is produced by the dairy bacterium Lactococcus lactis when aerobic respiration is activated by haem addition, and comprises ∼70% of carbohydrate degradation products. Here we investigate the targets of acetoin toxicity, and determine how acetoin impacts L. lactis physiology and survival. Acetoin caused damage to DNA and proteins, which related to reactivity of its keto group. Acetoin stress was reflected in proteome profiles, which revealed changes in lipid metabolic proteins. Acetoin provoked marked changes in fatty acid composition, with massive accumulation of cycC19:0 cyclopropane fatty acid at the expense of its unsaturated C18:1 fatty acid precursor. Deletion of the cfa gene, encoding the cycC19:0 synthase, sensitized cells to acetoin stress. Acetoin-resistant transposon mutagenesis revealed a hot spot in the high affinity phosphate transporter operon pstABCDEF, which is known to increase resistance to multiple stresses. This work reveals the causes and consequences of acetoin stress on L. lactis, and may facilitate control of lactic acid bacteria production in technological processes. IMPORTANCE Acetoin, 3-hydroxyl,2-butanone, has diverse uses in chemical industry, agriculture, and dairy industries as a volatile compound that generates aromas. In bacteria, it can be produced in high amount by Lactococcus lactis when it grows under aerobic respiration. However, acetoin production can be toxic and detrimental for growth and/or survival. Our results showed that it damages DNA and proteins via its keto group. We also showed that acetoin modifies membrane fatty acid composition with the production of cyclopropane C19:0 fatty acid at the expense of an unsaturated C18:1. We isolated mutants more resistant to acetoin than the wild-type strain. All of them mapped to a single locus pstABCDEF operon, suggesting a simple means to limit acetoin toxicity in dairy bacteria and to improve its production.
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2
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Fan X, Bai Y, Fan TP, Zheng X, Cai Y. A single point mutation engineering for changing the substrate specificity of d-lactate dehydrogenase from Lactobacillus fermentum. Lebensm Wiss Technol 2021. [DOI: 10.1016/j.lwt.2021.112209] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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3
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Guo J, Higgins MA, Daniel-Ivad P, Ryan KS. An Asymmetric Reductase That Intercepts Acyclic Imino Acids Produced in Situ by a Partner Oxidase. J Am Chem Soc 2019; 141:12258-12267. [PMID: 31298853 DOI: 10.1021/jacs.9b03307] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Acyclic imines are unstable in aqueous conditions. For this reason, known imine reductases, which enable the synthesis of chiral amines, mainly intercept stable cyclic imines. Here we report the detailed biochemical and structural characterization of Bsp5, an imino acid reductase from the d-2-hydroxyacid dehydrogenase family that reduces acyclic imino acids produced in situ by a partner oxidase. We determine a 1.6 Å resolution structure of Bsp5 in complex with d-arginine and coenzyme NADPH. Combined with mutagenesis work, our study reveals the minimal structural constraints for its biosynthetic activity. Furthermore, we demonstrate that Bsp5 can intercept more complex products from an alternate oxidase partner, suggesting that this oxidase-imino acid reductase pair could be evolved for biocatalytic conversion of l-amino acids to d-amino acids.
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Affiliation(s)
- Jin Guo
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z4 , Canada
| | - Melanie A Higgins
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z4 , Canada
| | - Phillip Daniel-Ivad
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z4 , Canada
| | - Katherine S Ryan
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z4 , Canada
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4
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Matelska D, Shabalin IG, Jabłońska J, Domagalski MJ, Kutner J, Ginalski K, Minor W. Classification, substrate specificity and structural features of D-2-hydroxyacid dehydrogenases: 2HADH knowledgebase. BMC Evol Biol 2018; 18:199. [PMID: 30577795 PMCID: PMC6303947 DOI: 10.1186/s12862-018-1309-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 11/27/2018] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND The family of D-isomer specific 2-hydroxyacid dehydrogenases (2HADHs) contains a wide range of oxidoreductases with various metabolic roles as well as biotechnological applications. Despite a vast amount of biochemical and structural data for various representatives of the family, the long and complex evolution and broad sequence diversity hinder functional annotations for uncharacterized members. RESULTS We report an in-depth phylogenetic analysis, followed by mapping of available biochemical and structural data on the reconstructed phylogenetic tree. The analysis suggests that some subfamilies comprising enzymes with similar yet broad substrate specificity profiles diverged early in the evolution of 2HADHs. Based on the phylogenetic tree, we present a revised classification of the family that comprises 22 subfamilies, including 13 new subfamilies not studied biochemically. We summarize characteristics of the nine biochemically studied subfamilies by aggregating all available sequence, biochemical, and structural data, providing comprehensive descriptions of the active site, cofactor-binding residues, and potential roles of specific structural regions in substrate recognition. In addition, we concisely present our analysis as an online 2HADH enzymes knowledgebase. CONCLUSIONS The knowledgebase enables navigation over the 2HADHs classification, search through collected data, and functional predictions of uncharacterized 2HADHs. Future characterization of the new subfamilies may result in discoveries of enzymes with novel metabolic roles and with properties beneficial for biotechnological applications.
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Affiliation(s)
- Dorota Matelska
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908, USA.,Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, Zwirki i Wigury 93, 02-089, Warsaw, Poland
| | - Ivan G Shabalin
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908, USA.,Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA, 22908, USA
| | - Jagoda Jabłońska
- Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, Zwirki i Wigury 93, 02-089, Warsaw, Poland
| | - Marcin J Domagalski
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908, USA.,Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA, 22908, USA
| | - Jan Kutner
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908, USA.,Laboratory for Structural and Biochemical Research, Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Zwirki i Wigury 101, 02-089, Warsaw, Poland
| | - Krzysztof Ginalski
- Laboratory of Bioinformatics and Systems Biology, Centre of New Technologies, University of Warsaw, Zwirki i Wigury 93, 02-089, Warsaw, Poland.
| | - Wladek Minor
- Department of Molecular Physiology and Biological Physics, University of Virginia, 1340 Jefferson Park Avenue, Charlottesville, VA, 22908, USA. .,Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA, 22908, USA. .,Department of Chemistry, University of Warsaw, Ludwika Pasteura 1, 02-093, Warsaw, Poland.
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5
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Furukawa N, Miyanaga A, Nakajima M, Taguchi H. Structural Basis of Sequential Allosteric Transitions in Tetrameric d-Lactate Dehydrogenases from Three Gram-Negative Bacteria. Biochemistry 2018; 57:5388-5406. [PMID: 30149697 DOI: 10.1021/acs.biochem.8b00557] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
d-Lactate dehydrogenases (d-LDHs) from Fusobacterium nucleatum (FnLDH) and Escherichia coli (EcLDH) exhibit positive cooperativity in substrate binding, and the Pseudomonas aeruginosa enzyme (PaLDH) shows negatively cooperative substrate binding. The apo and ternary complex structures of FnLDH and PaLDH have been determined together with the apo-EcLDH structure. The three enzymes consistently form homotetrameric structures with three symmetric axes, the P-, Q-, and R-axes, unlike Lactobacillus d-LDHs, P-axis-related dimeric enzymes, although apo-FnLDH and EcLDH form asymmetric and distorted quaternary structures. The tetrameric structure allows apo-FnLDH and EcLDH to form wide intersubunit contact surfaces between the opened catalytic domains of the two Q-axis-related subunits in coordination with their asymmetric and distorted quaternary structures. These contact surfaces comprise intersubunit hydrogen bonds and hydrophobic interactions and likely prevent the domain closure motion during initial substrate binding. In contrast, apo-PaLDH possesses a highly symmetrical quaternary structure and partially closed catalytic domains that are favorable for initial substrate binding and forms virtually no intersubunit contact surface between the catalytic domains, which present their negatively charged surfaces to each other at the subunit interface. Complex FnLDH and PaLDH possess highly symmetrical quaternary structures with closed forms of the catalytic domains, which are separate from each other at the subunit interface. Structure-based mutations successfully converted the three enzymes to their dimeric forms, which exhibited no significant cooperativity in substrate binding. These observations indicate that the three enzymes undergo typical sequential allosteric transitions to exhibit their distinctive allosteric functions through the tetrameric structures.
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Affiliation(s)
- Nayuta Furukawa
- Department of Applied Biological Science, Faculty of Science and Technology , Tokyo University of Science , 2641 Yamazaki , Noda , Chiba 278-8510 , Japan.,Department of Applied Life Sciences , Niigata University of Pharmacy and Applied Life Sciences , 265-1 Higashijima , Akiha-ku, Niigata 956-8603 , Japan
| | - Akimasa Miyanaga
- Department of Chemistry , Tokyo Institute of Technology , 2-12-1 O-okayama , Meguro-ku, Tokyo 152-8551 , Japan
| | - Masahiro Nakajima
- Department of Applied Biological Science, Faculty of Science and Technology , Tokyo University of Science , 2641 Yamazaki , Noda , Chiba 278-8510 , Japan
| | - Hayao Taguchi
- Department of Applied Biological Science, Faculty of Science and Technology , Tokyo University of Science , 2641 Yamazaki , Noda , Chiba 278-8510 , Japan
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6
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Jia B, Pu ZJ, Tang K, Jia X, Kim KH, Liu X, Jeon CO. Catalytic, Computational, and Evolutionary Analysis of the d-Lactate Dehydrogenases Responsible for d-Lactic Acid Production in Lactic Acid Bacteria. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2018; 66:8371-8381. [PMID: 30008205 DOI: 10.1021/acs.jafc.8b02454] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
d-Lactate dehydrogenase (d-LDH) catalyzes the reversible reaction pyruvate + NADH + H+ ↔ lactate + NAD+, which is a principal step in the production of d-lactate in lactic acid bacteria. In this study, we identified and characterized the major d-LDH (d-LDH1) from three d-LDHs in Leuconostoc mesenteroides, which has been extensively used in food processing. A molecular simulation study of d-LDH1 showed that the conformation changes during substrate binding. During catalysis, Tyr101 and Arg235 bind the substrates by hydrogen bonds and His296 acts as a general acid/base for proton transfer. These residues are also highly conserved and have coevolved. Point mutations proved that the substrate binding sites and catalytic site are crucial for enzyme activity. Network and phylogenetic analyses indicated that d-LDH1 and the homologues are widely distributed but are most abundant in bacteria and fungi. This study expands the understanding of the functions, catalytic mechanism, and evolution of d-LDH.
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Affiliation(s)
- Baolei Jia
- State Key Laboratory of Biobased Material and Green Papermaking, School of Bioengineering , Qilu University of Technology (Shandong Academy of Sciences) , Jinan 250353 , China
- Department of Life Science , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Zhong Ji Pu
- School of Life Science and Biotechnology , Dalian University of Technology , Dalian 116024 , China
| | - Ke Tang
- State Key Laboratory of Biobased Material and Green Papermaking, School of Bioengineering , Qilu University of Technology (Shandong Academy of Sciences) , Jinan 250353 , China
| | - Xiaomeng Jia
- Department of Life Science , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Kyung Hyun Kim
- Department of Life Science , Chung-Ang University , Seoul 06974 , Republic of Korea
| | - Xinli Liu
- State Key Laboratory of Biobased Material and Green Papermaking, School of Bioengineering , Qilu University of Technology (Shandong Academy of Sciences) , Jinan 250353 , China
| | - Che Ok Jeon
- Department of Life Science , Chung-Ang University , Seoul 06974 , Republic of Korea
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7
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Singh RK, Raj I, Pujari R, Gourinath S. Crystal structures and kinetics of Type III 3-phosphoglycerate dehydrogenase reveal catalysis by lysine. FEBS J 2014; 281:5498-512. [PMID: 25294608 DOI: 10.1111/febs.13091] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Revised: 09/11/2014] [Accepted: 09/30/2014] [Indexed: 11/29/2022]
Abstract
D-Phosphoglycerate dehydrogenase (PGDH) catalyzes the first committed step of the phosphorylated serine biosynthesis pathway. Here, we report for the first time, the crystal structures of Type IIIK PGDH from Entamoeba histolytica in the apo form, as well as in complexes with substrate (3-phosphoglyceric acid) and cofactor (NAD(+) ) to 2.45, 1.8 and 2.2 Å resolution, respectively. Comparison of the apo structure with the substrate-bound structure shows that the substrate-binding domain is rotated by ~ 20° to close the active-site cleft. The cofactor-bound structure also shows a closed-cleft conformation, in which NAD(+) is bound to the nucleotide-binding domain and a formate ion occupies the substrate-binding site. Superposition of the substrate- and cofactor-bound structures represents a snapshot of the enzyme in the active form, where C2 of the substrate and C4N of the cofactor are 2.2 Å apart, and the amino group of Lys263 is close enough to the substrate to remove the proton from the hydroxyl group of PGA, indicating the role of Lys in the catalysis. Mutation of Lys263 to Ala yields just 0.8% of the specific activity of the wild-type enzyme, revealing that Lys263 indeed plays an integral role in the catalytic activity. The detectable activity of the mutant, however, indicates that after 20° rotation of the substrate-binding domain, the resulting positions of the substrate and cofactor are sufficiently close to make a productive reaction.
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Affiliation(s)
- Rohit K Singh
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
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8
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Holton SJ, Anandhakrishnan M, Geerlof A, Wilmanns M. Structural characterization of a D-isomer specific 2-hydroxyacid dehydrogenase from Lactobacillus delbrueckii ssp. bulgaricus. J Struct Biol 2012; 181:179-84. [PMID: 23110853 DOI: 10.1016/j.jsb.2012.10.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Revised: 09/29/2012] [Accepted: 10/01/2012] [Indexed: 10/27/2022]
Abstract
Hydroxyacid dehydrogenases, responsible for the stereospecific conversion of 2-keto acids to 2-hydroxyacids in lactic acid producing bacteria, have a range of biotechnology applications including antibiotic synthesis, flavor development in dairy products and the production of valuable synthons. The genome of Lactobacillus delbrueckii ssp. bulgaricus, a member of the heterogeneous group of lactic acid bacteria, encodes multiple hydroxyacid dehydrogenases whose structural and functional properties remain poorly characterized. Here, we report the apo and coenzyme NAD⁺ complexed crystal structures of the L. bulgaricusD-isomer specific 2-hydroxyacid dehydrogenase, D2-HDH. Comparison with closely related members of the NAD-dependent dehydrogenase family reveals that whilst the D2-HDH core fold is structurally conserved, the substrate-binding site has a number of non-canonical features that may influence substrate selection and thus dictate the physiological function of the enzyme.
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Affiliation(s)
- Simon J Holton
- EMBL c/o DESY, Notkestrasse 85, D-22603 Hamburg, Germany.
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9
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Ishikura Y, Tsuzuki S, Takahashi O, Tokuda C, Nakanishi R, Shinoda T, Taguchi H. Recognition site for the side chain of 2-ketoacid substrate in d-lactate dehydrogenase. J Biochem 2009; 138:741-9. [PMID: 16428303 DOI: 10.1093/jb/mvi170] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Replacement of Tyr52 with Val or Ala in Lactobacillus pentosus d-lactate dehydrogenase induced high activity and preference for large aliphatic 2-ketoacids and phenylpyruvate. On the other hand, replacements with Arg, Thr or Asp severely reduced the enzyme activity, and the Tyr52Arg enzyme, the only one that exhibited significant enzyme activity, showed a similar substrate preference to the Tyr52Val and Tyr52Ala enzymes. Replacement of Phe299 with Gly or Ser greatly reduced the enzyme activity with less marked change in the substrate preference. Except for the Phe299Ser enzyme, these mutant enzymes with low catalytic activity consistently stimulated NADH oxidation in the absence of 2-ketoacid substrates. However, the double mutant enzymes, Tyr52Arg/Phe299Gly and Tyr52Thr/Phe299Ser, did not exhibit synergically decreased enzyme activity or the substrate-independent NADH oxidation, but rather increased activities toward certain 2-ketoacid substrates. These results indicate that the coordinative combination of amino acid residues at two positions is pivotal in both the functional recognition of the 2-ketoacid side chain and the protection of the bound NADH molecule from the solvent. Multiplicity in such combinations appears to provide d-LDH-related 2-hydroxyacid dehydrogenases with a great variety of catalytic and physiological functions.
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Affiliation(s)
- Yoshirou Ishikura
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510
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10
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The D-2-hydroxyacid dehydrogenase incorrectly annotated PanE is the sole reduction system for branched-chain 2-keto acids in Lactococcus lactis. J Bacteriol 2008; 191:873-81. [PMID: 19047348 DOI: 10.1128/jb.01114-08] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Hydroxyacid dehydrogenases of lactic acid bacteria, which catalyze the stereospecific reduction of branched-chain 2-keto acids to 2-hydroxyacids, are of interest in a variety of fields, including cheese flavor formation via amino acid catabolism. In this study, we used both targeted and random mutagenesis to identify the genes responsible for the reduction of 2-keto acids derived from amino acids in Lactococcus lactis. The gene panE, whose inactivation suppressed hydroxyisocaproate dehydrogenase activity, was cloned and overexpressed in Escherichia coli, and the recombinant His-tagged fusion protein was purified and characterized. The gene annotated panE was the sole gene responsible for the reduction of the 2-keto acids derived from leucine, isoleucine, and valine, while ldh, encoding L-lactate dehydrogenase, was responsible for the reduction of the 2-keto acids derived from phenylalanine and methionine. The kinetic parameters of the His-tagged PanE showed the highest catalytic efficiencies with 2-ketoisocaproate, 2-ketomethylvalerate, 2-ketoisovalerate, and benzoylformate (V(max)/K(m) ratios of 6,640, 4,180, 3,300, and 2,050 U/mg/mM, respectively), with NADH as the exclusive coenzyme. For the reverse reaction, the enzyme accepted d-2-hydroxyacids but not l-2-hydroxyacids. Although PanE showed the highest degrees of identity to putative NADP-dependent 2-ketopantoate reductases (KPRs), it did not exhibit KPR activity. Sequence homology analysis revealed that, together with the d-mandelate dehydrogenase of Enterococcus faecium and probably other putative KPRs, PanE belongs to a new family of D-2-hydroxyacid dehydrogenases which is unrelated to the well-described D-2-hydroxyisocaproate dehydrogenase family. Its probable physiological role is to regenerate the NAD(+) necessary to catabolize branched-chain amino acids, leading to the production of ATP and aroma compounds.
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11
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Relyea HA, Vrtis JM, Woodyer R, Rimkus SA, van der Donk WA. Inhibition and pH dependence of phosphite dehydrogenase. Biochemistry 2005; 44:6640-9. [PMID: 15850397 DOI: 10.1021/bi047640p] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phosphite dehydrogenase (PTDH) catalyzes the NAD-dependent oxidation of phosphite to phosphate, a reaction that is 15 kcal/mol exergonic. The enzyme belongs to the family of D-hydroxy acid dehydrogenases. Five other family members that were analyzed do not catalyze the oxidation of phosphite, ruling out the possibility that this is a ubiquitous activity of these proteins. PTDH does not accept any alternative substrates such as thiophosphite, hydrated aldehydes, and methylphosphinate, and potential small nucleophiles such as hydroxylamine, fluoride, methanol, and trifluoromethanol do not compete with water in the displacement of the hydride from phosphite. The pH dependence of k(cat)/K(m,phosphite) is bell-shaped with a pK(a) of 6.8 for the acidic limb and a pK(a) of 7.8 for the basic limb. The pK(a) of 6.8 is assigned to the second deprotonation of phosphite. However, whether the dianionic form of phosphite is the true substrate is not clear since a reverse protonation mechanism is also consistent with the available data. Unlike k(cat)/K(m,phosphite), k(cat) and k(cat)/K(m,NAD) are pH-independent. Sulfite is a strong inhibitor of PTDH that is competitive with respect to phosphite and uncompetitive with respect to NAD(+). Incubation of the enzyme with NAD(+) and low concentrations of sulfite results in a covalent adduct between NAD(+) and sulfite in the active site of the enzyme that binds very tightly. Fluorescent titration studies provided the apparent dissociation constants for NAD(+), NADH, sulfite, and the sulfite-NAD(+) adduct. Substrate isotope effect studies with deuterium-labeled phosphite resulted in small normal isotope effects (1.4-2.1) on both k(cat) and k(cat)/K(m,phosphite) at pH 7.25 and 8.0. Solvent isotope effects (SIEs) on k(cat) are similar in size; however, the SIE of k(cat)/K(m,phosphite) at pH 7.25 is significantly larger (4.4), whereas at pH 8.0, it is the inverse (0.6). The pH-rate profile of k(cat)/K(m,phosphite), which predicts that the observed SIEs will have a significant thermodynamic origin, can account for these effects.
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Affiliation(s)
- Heather A Relyea
- Department of Chemistry, University of Illinois, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
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12
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Woodyer R, Wheatley JL, Relyea HA, Rimkus S, van der Donk WA. Site-directed mutagenesis of active site residues of phosphite dehydrogenase. Biochemistry 2005; 44:4765-74. [PMID: 15779903 DOI: 10.1021/bi047868c] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phosphite dehydrogenase (PTDH) catalyzes the unusual oxidation of phosphite to phosphate with the concomitant reduction of NAD(+) to NADH. PTDH shares significant amino acid sequence similarity with D-hydroxy acid dehydrogenases (DHs), including strongly conserved catalytic residues His292, Glu266, and Arg237. Site-directed mutagenesis studies corroborate the essential role of His292 as all mutants of this residue were completely inactive. Histidine-selective inactivation studies with diethyl pyrocarbonate provide further evidence regarding the importance of His292. This residue is most likely the active site base that deprotonates the water nucleophile. Kinetic analysis of mutants in which Arg237 was changed to Leu, Lys, His, and Gln revealed that Arg237 is involved in substrate binding. These results agree with the typical role of this residue in D-hydroxy acid DHs. However, Glu266 does not play the typical role of increasing the pK(a) of His292 to enhance substrate binding and catalysis as the Glu266Gln mutant displayed an increased k(cat) and unchanged pH-rate profile compared to those of wild-type PTDH. The role of Glu266 is likely the positioning of His292 and Arg237 with which it forms hydrogen bonds in a homology model. Homology modeling suggests that Lys76 may also be involved in substrate binding, and this postulate is supported by mutagenesis studies. All mutants of Lys76 display reduced activity with large effects on the K(m) for phosphite, and Lys76Cys could be chemically rescued by alkylation with 2-bromoethylamine. Whereas a positively charged residue is absolutely essential for activity at the position of Arg237, Lys76 mutants that lacked a positively charged side chain still had activity, indicating that it is less important for binding and catalysis. These results highlight the versatility of nature's catalytic scaffolds, as a common framework with modest changes allows PTDH to catalyze its unusual nucleophilic displacement reaction and d-hydroxy acid DHs to oxidize alcohols to ketones.
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Affiliation(s)
- Ryan Woodyer
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, Illinois 61801, USA
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13
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Shinoda T, Arai K, Shigematsu-Iida M, Ishikura Y, Tanaka S, Yamada T, Kimber MS, Pai EF, Fushinobu S, Taguchi H. Distinct conformation-mediated functions of an active site loop in the catalytic reactions of NAD-dependent D-lactate dehydrogenase and formate dehydrogenase. J Biol Chem 2005; 280:17068-75. [PMID: 15734738 DOI: 10.1074/jbc.m500970200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The three-dimensional structures of NAD-dependent D-lactate dehydrogenase (D-LDH) and formate dehydrogenase (FDH), which resemble each other, imply that the two enzymes commonly employ certain main chain atoms, which are located on corresponding loop structures in the active sites of the two enzymes, for their respective catalytic functions. These active site loops adopt different conformations in the two enzymes, a difference likely attributable to hydrogen bonds with Asn97 and Glu141, which are also located at equivalent positions in D-LDH and FDH, respectively. X-ray crystallography at 2.4-A resolution revealed that replacement of Asn97 with Asp did not markedly change the overall protein structure but markedly perturbed the conformation of the active site loop in Lactobacillus pentosus D-LDH. The Asn97-->Asp mutant D-LDH exhibited virtually the same k(cat), but about 70-fold higher K(M) value for pyruvate than the wild-type enzyme. For Paracoccus sp. 12-A FDH, in contrast, replacement of Glu141 with Gln and Asn induced only 5.5- and 4.3-fold increases in the K(M) value, but 110 and 590-fold decreases in the k(cat) values for formate, respectively. Furthermore, these mutant FDHs, particularly the Glu141-->Asn enzyme, exhibited markedly enhanced catalytic activity for glyoxylate reduction, indicating that FDH is converted to a 2-hydroxy-acid dehydrogenase on the replacement of Glu141. These results indicate that the active site loops play different roles in the catalytic reactions of D-LDH and FDH, stabilization of substrate binding and promotion of hydrogen transfer, respectively, and that Asn97 and Glu141, which stabilize suitable loop conformations, are essential elements for proper loop functioning.
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Affiliation(s)
- Takeshi Shinoda
- Department of Applied Biological Science, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
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14
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Relyea HA, van der Donk WA. Mechanism and applications of phosphite dehydrogenase. Bioorg Chem 2005; 33:171-89. [PMID: 15888310 DOI: 10.1016/j.bioorg.2005.01.003] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2004] [Revised: 01/17/2005] [Accepted: 01/18/2005] [Indexed: 11/18/2022]
Abstract
Phosphite dehydrogenase catalyzes the NAD+-dependent oxidation of hydrogen phosphonate (common name phosphite) to phosphate in what amounts to a formal phosphoryl transfer reaction from hydride to hydroxide. This review places the enzyme in the context of phosphorus redox metabolism in nature and discusses the results of mechanistic investigations into its reaction mechanism. The potential of the enzyme as a NAD(P)H cofactor regeneration system is discussed as well as efforts to engineer the cofactor specificity of the protein.
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Affiliation(s)
- Heather A Relyea
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 S. Matthews Ave., Urbana, IL 61801, USA
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15
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Martins BM, Macedo-Ribeiro S, Bresser J, Buckel W, Messerschmidt A. Structural basis for stereo-specific catalysis in NAD(+)-dependent (R)-2-hydroxyglutarate dehydrogenase from Acidaminococcus fermentans. FEBS J 2005; 272:269-81. [PMID: 15634349 DOI: 10.1111/j.1432-1033.2004.04417.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
NAD(+)-dependent (R)-2-hydroxyglutarate dehydrogenase (HGDH) catalyses the reduction of 2-oxoglutarate to (R)-2-hydroxyglutarate and belongs to the d-2-hydroxyacid NAD(+)-dependent dehydrogenase (d-2-hydroxyacid dehydrogenase) protein family. Its crystal structure was determined by phase combination to 1.98 A resolution. Structure-function relationships obtained by the comparison of HGDH with other members of the d-2-hydroxyacid dehydrogenase family give a chemically satisfying view of the substrate stereoselectivity and catalytic requirements for the hydride transfer reaction. A model for substrate recognition and turnover is discussed. The HGDH active site architecture is structurally optimized to recognize and bind the negatively charged substrate 2-oxoglutarate. The structural position of the side chain of Arg52, and its counterparts in other family members, strongly correlates with substrate specificity towards substitutions at the C3 atom (linear or branched substrates). Arg235 interacts with the substrate's alpha-carboxylate and carbonyl groups, having a dual role in both substrate binding and activation, and the gamma-carboxylate group can dock at an arginine cluster. The proton-relay system built up by Glu264 and His297 permits His297 to act as acid-base catalyst and the 4Re-hydrogen from NADH is transferred as hydride to the carbonyl group Si-face leading to the formation of the correct enantiomer (R)-2-hydroxyglutarate.
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16
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Cloning and characterization of the lactate dehydrogenase genes fromLactobacillus sp. RKY2. BIOTECHNOL BIOPROC E 2004. [DOI: 10.1007/bf02942351] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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17
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Razeto A, Kochhar S, Hottinger H, Dauter M, Wilson KS, Lamzin VS. Domain closure, substrate specificity and catalysis of D-lactate dehydrogenase from Lactobacillus bulgaricus. J Mol Biol 2002; 318:109-19. [PMID: 12054772 DOI: 10.1016/s0022-2836(02)00086-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
NAD-dependent Lactobacillus bulgaricus D-Lactate dehydrogenase (D-LDHb) catalyses the reversible conversion of pyruvate into D-lactate. Crystals of D-LDHb complexed with NADH were grown and X-ray data collected to 2.2 A. The structure of D-LDHb was solved by molecular replacement using the dimeric Lactobacillus helveticus D-LDH as a model and was refined to an R-factor of 20.7%. The two subunits of the enzyme display strong asymmetry due to different crystal environments. The opening angles of the two catalytic domains with respect to the core coenzyme binding domains differ by 16 degrees. Subunit A is in an "open" conformation typical for a dehydrogenase apo enzyme and subunit B is "closed". The NADH-binding site in subunit A is only 30% occupied, while in subunit B it is fully occupied and there is a sulphate ion in the substrate-binding pocket. A pyruvate molecule has been modelled in the active site and its orientation is in agreement with existing kinetic and structural data. On domain closure, a cluster of hydrophobic residues packs tightly around the methyl group of the modelled pyruvate molecule. At least three residues from this cluster govern the substrate specificity. Substrate binding itself contributes to the stabilisation of domain closure and activation of the enzyme. In pyruvate reduction, D-LDH can adapt another protonated residue, a lysine residue, to accomplish the role of the acid catalyst His296. Required lowering of the lysine pK(a) value is explained on the basis of the H296K mutant structure.
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Affiliation(s)
- Adelia Razeto
- European Molecular Biology Laboratory Hamburg Outstation, c/o DESY, Notkestrasse 85, 22603 Hamburg, Germany.
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18
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Marshall CG, Zolli M, Wright GD. Molecular mechanism of VanHst, an alpha-ketoacid dehydrogenase required for glycopeptide antibiotic resistance from a glycopeptide producing organism. Biochemistry 1999; 38:8485-91. [PMID: 10387095 DOI: 10.1021/bi982843x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The vancomycin resistance enzyme VanH is an alpha-ketoacid dehydrogenase that stereospecifically reduces pyruvate to D-lactate, which is required for the synthesis of the depsipeptide D-alanine-D-lactate. This compound then forms an integral part of the bacterial cell wall replacing the vancomycin target dipeptide D-alanine-D-alanine, thus the presence of VanH is essential for glycopeptide resistance. In this work, the VanH homologue from the glycopeptide antibiotic producing organism Streptomyces toyocaensis NRRL 15009, VanHst, has been overexpressed in Escherichia coli and purified, and its substrate specificity and mechanism were probed by steady-state kinetic methods and site-directed mutagenesis. The enzyme is highly efficient at pyruvate reduction with kcat/Km = 1.3 x 10(5) M-1 s-1 and has a more restricted alpha-ketoacid substrate specificity than VanH from vancomycin resistant enterococci (VRE). Conversely, VanHst shows no preference between NADH and NADPH while VanH from VRE prefers NADPH. The kinetic mechanism for VanHst was determined using product and dead-end inhibitors to be ordered BiBi with NADH binding first followed by pyruvate and products leaving in the order D-lactate, NAD+. Site-directed mutagenesis indicated that Arg237 plays a role in pyruvate binding and catalysis and that His298 is a candidate for an active-site proton donor. Glu266, which has been suggested to modulate the pKa of the catalytic His in other D-lactate dehydrogenases, was found to fulfill a similar role in VanHst, lowering a pKa value of kcat/Km nearly 2 units. These results now provide the framework for additional structure and inhibitor design work on the VanH family of antibiotic resistance enzymes.
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Affiliation(s)
- C G Marshall
- Antimicrobial Research Centre, Department of Biochemistry, McMaster University, Hamilton, ON, Canada
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19
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Marshall CG, Lessard IA, Park I, Wright GD. Glycopeptide antibiotic resistance genes in glycopeptide-producing organisms. Antimicrob Agents Chemother 1998; 42:2215-20. [PMID: 9736537 PMCID: PMC105782 DOI: 10.1128/aac.42.9.2215] [Citation(s) in RCA: 172] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanism of high-level resistance to vancomycin in enterococci consists of the synthesis of peptidoglycan terminating in D-alanyl-D-lactate instead of the usual D-alanyl-D-alanine. This alternate cell wall biosynthesis pathway is ensured by the collective actions of three enzymes: VanH, VanA, and VanX. The origin of this resistance mechanism is unknown. We have cloned three genes encoding homologs of VanH, VanA, and VanX from two organisms which produce glycopeptide antibiotics: the A47934 producer Streptomyces toyocaensis NRRL 15009 and the vancomycin producer Amycolatopsis orientalis C329.2. The predicted amino acid sequences are highly similar to those found in VRE: 54 to 61% identity for VanH, 59 to 63% identity for VanA, and 61 to 64% identity for VanX. Furthermore, the orientations of the genes, vanH, vanA, and vanX, are identical to the orientations found in vancomycin-resistant enterococci. Southern analysis of total DNA from other glycopeptide-producing organisms, A. orientalis 18098 (chloro-eremomycin producer), A. orientalis subsp. lurida (ristocetin producer), and Amycolatopsis coloradensis subsp. labeda (teicoplanin and avoparcin producer), with a probe derived from the vanH, vanA, and vanX cluster from A. orientalis C329.2 revealed cross-hybridizing DNA in all strains. In addition, the vanH, vanA, vanX cluster was amplified from all glycopeptide-producing organisms by PCR with degenerate primers complementary to conserved regions in VanH and VanX. Thus, this gene sequence is common to all glycopeptide producers tested. These results suggest that glycopeptide-producing organisms may have been the source of resistance genes in vancomycin-resistant enterococci.
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Affiliation(s)
- C G Marshall
- Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
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20
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Stoll VS, Manohar AV, Gillon W, MacFarlane EL, Hynes RC, Pai EF. A thioredoxin fusion protein of VanH, a D-lactate dehydrogenase from Enterococcus faecium: cloning, expression, purification, kinetic analysis, and crystallization. Protein Sci 1998; 7:1147-55. [PMID: 9605319 PMCID: PMC2144001 DOI: 10.1002/pro.5560070508] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The gene encoding the vancomycin resistance protein VanH from Enterococcus faecium, a D-lactate dehydrogenase, has been cloned into a thioredoxin expression system (pTRxFus) and expressed as a fusion protein. The use of several other expression systems yielded only inclusion bodies from which no functional protein could be recovered. Experiments to remove the thioredoxin moiety by enterokinase cleavage at the engineered recognition site under a variety of conditions resulted in nonspecific proteolysis and inactivation of the protein. The intact fusion protein was, therefore, used for kinetic studies and crystallization trials. It has been purified to greater than 90% homogeneity by ammonium sulfate precipitation followed by phenyl Sepharose chromatography. Based on k(cat)/KM for pyruvate, it is 20% as active as native VanH. Michaelis constants for NADPH, NADH, and pyruvate, of approximately 3.5 microM, 19.0 microM, and 1.5 mM, respectively, were comparable to those reported for the native VanH (Bugg TDH et al., 1991, Biochemistry 30:10408-10415). Like native VanH, maximum activity of the fusion protein requires the presence of an anion (phosphate or acetate), however, in addition, a strongly reducing environment is needed for optimal efficacy. Competitive inhibition constants for ADP-ribose, NAD+, and oxamate have also been determined. Crystallization by hanging drop vapor diffusion produced two different crystal forms, one hexagonal and the other tetragonal. Flash-frozen crystals of the tetragonal form diffracted to 3.0 A resolution at a synchrotron radiation source.
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Affiliation(s)
- V S Stoll
- Department of Biochemistry, University of Toronto, Ontario, Canada
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21
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Dengler U, Niefind K, Kiess M, Schomburg D. Crystal structure of a ternary complex of D-2-hydroxyisocaproate dehydrogenase from Lactobacillus casei, NAD+ and 2-oxoisocaproate at 1.9 A resolution. J Mol Biol 1997; 267:640-60. [PMID: 9126843 DOI: 10.1006/jmbi.1996.0864] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
D-2-hydroxyisocaproate dehydrogenase (D-HicDH) from Lactobacillus casei is a homodimer with 333 amino acids and a molecular mass of 37 kDa per subunit. The enzyme belongs to the protein family of NAD+-dependent D-2-hydroxycarboxylate dehydrogenases and within this family to the subgroup of D-lactate dehydrogenases (D-LDHs). Compared with other D-LDHs D-HicDH is characterized by a very low specificity regarding size and chemical constitution of the accepted D-2-hydroxycarboxylates. Hexagonal crystals of recombinant D-HicDH in the presence of NAD+ and 2-oxoisocaproate (4-methyl-2-oxopentanoate) were grown with ammonium sulphate as precipitating agent. The structure of these crystals was solved by molecular replacement and refined to a final R-factor of 19.6% for all measured X-ray reflections in the resolution range (infinity to 1.86 A). Both NAD+ and 2-oxoisocaproate were identified in the electron density map; binding of the latter in the active site, however, competes with a sulphate ion, which is also defined by electron density. Additionally the final model contains 182 water molecules and a second sulphate ion. The binding of both an in vitro substrate and the natural cosubstrate in the active site provides substantial insight into the catalytic mechanism and allows us to assess previously published active site models for this enzyme family, in particular the two most controversial points, the role of the conserved Arg234 and substrate binding. Furthermore the overall topology and details of the D-HicDH structure are described, discussed against the background of homologous structures and compared with one closely and one distantly related protein.
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Affiliation(s)
- U Dengler
- Gesellschaft fur Biotechnologische Forschung (GBF), Abteilung Molekulare Strukturforschung, Braunschweig, Germany
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22
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Bernard N, Johnsen K, Gelpi JL, Alvarez JA, Ferain T, Garmyn D, Hols P, Cortes A, Clarke AR, Holbrook JJ, Delcour J. D-2-hydroxy-4-methylvalerate dehydrogenase from Lactobacillus delbrueckii subsp. bulgaricus. II. Mutagenic analysis of catalytically important residues. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 244:213-9. [PMID: 9063466 DOI: 10.1111/j.1432-1033.1997.00213.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Five residues involved in catalysis and coenzyme binding have been identified in D-2-hydroxy-4-methylvalerate dehydrogenase from Lactobacillus delbrueckii subsp. bulgaricus by using biochemical and genetical methods. Enzyme inactivation with diethylpyrocarbonate indicated that a single histidine residue was involved in catalysis. Since H296 is the only conserved histidine in the whole family of NAD-dependent D-2-hydroxyacid dehydrogenases, we constructed the H296Q and H296S mutants and showed that their catalytic efficiencies were reduced 10(5)-fold compared with the wild-type enzyme. This low residual activity was shown to be insensitive to diethylpyrocarbonate. Taken together these data demonstrate that H296 is responsible for proton exchange in the redox reaction. Two acidic residues (D259 and E264) were candidates for maintaining H296 in the protonated state and their roles were examined by mutagenesis. The D259N and E264Q mutant enzymes both showed similar and large reductions in their Kcat/K(m) ratios (200-800-fold, depending on pH), indicating that either D259 or E264 (or both) could partner H296. The conserved R235 residue was a candidate for binding the alpha-carboxyl group of the substrate and it was changed to lysine. The R235K mutant showed a 104-fold reduced Kcat/K(m) due to both an increased K(m) and a reduced Kcat for 2-oxo-4-methylvalerate. Thus R235 plays a role in binding the substrate carboxylate similar to R171 in the L-lactate dehydrogenases. Finally, we constructed the H205Q mutant to test the role of this partially conserved histidine residue (in 10/13 enzymes of the family). This mutant enzyme displayed a 7.7-fold increased Kcat and a doubled catalytic efficiency at pH 5, was as sensitive to diethylpyrocarbonate as the wild-type but showed a sevenfold increased K(m) for NADH and a 100-fold increase in Kd for NADH together with 10-30-fold lower substrate inhibition. The transient kinetic behaviour of the H205Q mutant is as predicted from our previous study on the enzymatic mechanism of D-2-hydroxy-4-methylvalerate dehydrogenase which showed that coenzyme binding is highly pH dependent and indicated that release of the oxidised coenzyme is a significant component of the rate-limiting processes in catalysis at pH 6.5.
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Affiliation(s)
- N Bernard
- Unité de Génétique, Université catholique de Louvain, Louvain-la-Neuve, Belgium
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23
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Krell T, Horsburgh MJ, Cooper A, Kelly SM, Coggins JR. Localization of the active site of type II dehydroquinases. Identification of a common arginine-containing motif in the two classes of dehydroquinases. J Biol Chem 1996; 271:24492-7. [PMID: 8798709 DOI: 10.1074/jbc.271.40.24492] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
A novel method based on electrospray mass spectrometry (Krell, T., Pitt, A. R., and Coggins, J. R. (1995) FEBS Lett. 360, 93-96) has been used to localize active site residues in the type I and type II dehydroquinases. Both enzymes have essential hyper-reactive arginine residues, and the type II enzymes have an essential tyrosine residue. The essential hyper-reactive Arg-23 of the Streptomyces coelicolor type II enzyme has been replaced by lysine, glutamine, and alanine residues. The mutant enzymes were purified and shown by CD spectroscopy to be structurally similar to the wild-type enzyme. All three mutant enzymes were much less active, for example the kcat of the R23A mutant was 30,000-fold reduced. The mutants all had reduced Km values, indicating stronger substrate binding, which was confirmed by isothermal titration calorimetry experiments. A role for Arg-23 in the stabilization of a carbanion intermediate is proposed. Comparison of the amino acid sequence around the hyper-reactive arginine residues of the two classes of enzymes indicates that there is a conserved structural motif that might reflect a common substrate binding fold at the active center of these two classes of enzyme.
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Affiliation(s)
- T Krell
- Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, University of Glasgow, Scotland, United Kingdom
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24
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Stoll VS, Kimber MS, Pai EF. Insights into substrate binding by D-2-ketoacid dehydrogenases from the structure of Lactobacillus pentosus D-lactate dehydrogenase. Structure 1996; 4:437-47. [PMID: 8740366 DOI: 10.1016/s0969-2126(96)00049-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
BACKGROUND D-Lactate dehydrogenases (D-LDHs) and L-lactate dehydrogenases (L-LDHs) catalyze a reaction differing only in the chirality of the product. Both enzymes utilize the same kind of amino acid side chains in substrate binding and catalysis. Models based on D-LDH-related enzymes propose that these side chains assume identical roles in both enzymes with their active sites related by a simple geometrical relationship such as a mirror plane. RESULTS The crystal structure of the homodimeric D-LDH from Lactobacillus pentosus has been determined to 2.6 A resolution by multiple isomorphous replacement methods and the resulting molecular model refined to an R-factor of 19.1%. Topologically, the enzyme is closely related to other D-2-ketoacid dehydrogenase enzymes. Each subunit comprises two domains enclosing a deep cleft containing the active site. Substrate binding and domain closure have been modelled. CONCLUSIONS Comparison of the D-LDH structure with other members of the protein family and with the L-specific enzyme has confirmed that no overall structural relationship exists between the L-LDH and D-LDH enzymes - they belong to distinct protein classes. The small size of the ketoacid substrate and the very restricted number of functionally appropriate side chains will constrain the choice of amino acids and their placement in the active site. Our models imply that although the same kinds of amino acids are involved in substrate binding their exact chemical role might differ in the two dehydrogenases.
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Affiliation(s)
- V S Stoll
- Department of Biochemistry, University of Toronto, Ontario, Canada
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Vinals C, De Bolle X, Depiereux E, Feytmans E. Knowledge-based modeling of the D-lactate dehydrogenase three-dimensional structure. Proteins 1995; 21:307-18. [PMID: 7567953 DOI: 10.1002/prot.340210405] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A three-dimensional structure of the NAD-dependent D-lactate dehydrogenase of Lactobacillus bulgaricus is modeled using the structure of the formate dehydrogenase of Pseudomonas sp. as template. Both sequences share only 22% of identical residues. Regions for knowledge-based modeling are defined from the structurally conserved regions predicted by multiple alignment of a set of related protein sequences with low homology. The model of the D-LDH subunit shows, as for the formate dehydrogenase, an alpha/beta structure, with a catalytic domain and a coenzyme binding domain. It points out the catalytic histidine (His-296) and supports the hypothetical catalytic mechanism. It also suggests that the other residues involved in the active site are Arg-235, possibly involved in the binding of the carboxyl group of the pyruvate, and Phe-299, a candidate for stabilizing the methyl group of the substrate.
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Affiliation(s)
- C Vinals
- Facultés Universitaires Notre Dame de la Paix, Namur, Belgium
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