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Bayle K, Akoka S, Remaud GS, Robins RJ. Nonstatistical 13C distribution during carbon transfer from glucose to ethanol during fermentation is determined by the catabolic pathway exploited. J Biol Chem 2015; 290:4118-28. [PMID: 25538251 PMCID: PMC4326821 DOI: 10.1074/jbc.m114.621441] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/22/2014] [Indexed: 11/06/2022] Open
Abstract
During the anaerobic fermentation of glucose to ethanol, the three micro-organisms Saccharomyces cerevisiae, Zymomonas mobilis, and Leuconostoc mesenteroides exploit, respectively, the Embden-Meyerhof-Parnas, the Entner-Doudoroff, and the reductive pentose phosphate pathways. Thus, the atoms incorporated into ethanol do not have the same affiliation to the atomic positions in glucose. The isotopic fractionation occurring in each pathway at both the methylene and methyl positions of ethanol has been investigated by isotopic quantitative (13)C NMR spectrometry with the aim of observing whether an isotope redistribution characteristic of the enzymes active in each pathway can be measured. First, it is found that each pathway has a unique isotope redistribution signature. Second, for the methylene group, a significant apparent kinetic isotope effect is only found in the reductive pentose phosphate pathway. Third, the apparent kinetic isotope effects related to the methyl group are more pronounced than for the methylene group. These findings can (i) be related to known kinetic isotope effects of some of the enzymes concerned and (ii) give indicators as to which steps in the pathways are likely to be influencing the final isotopic composition in the ethanol.
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Affiliation(s)
- Kevin Bayle
- From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France
| | - Serge Akoka
- From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France
| | - Gérald S Remaud
- From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France
| | - Richard J Robins
- From the Elucidation of Biosynthesis by Isotopic Spectrometry Group, CEISAM, UMR 6230, CNRS-University of Nantes, BP 99208, F-44322 Nantes, France
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Dellero Y, Mauve C, Boex-Fontvieille E, Flesch V, Jossier M, Tcherkez G, Hodges M. Experimental evidence for a hydride transfer mechanism in plant glycolate oxidase catalysis. J Biol Chem 2014; 290:1689-98. [PMID: 25416784 DOI: 10.1074/jbc.m114.618629] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In plants, glycolate oxidase is involved in the photorespiratory cycle, one of the major fluxes at the global scale. To clarify both the nature of the mechanism and possible differences in glycolate oxidase enzyme chemistry from C3 and C4 plant species, we analyzed kinetic parameters of purified recombinant C3 (Arabidopsis thaliana) and C4 (Zea mays) plant enzymes and compared isotope effects using natural and deuterated glycolate in either natural or deuterated solvent. The (12)C/(13)C isotope effect was also investigated for each plant glycolate oxidase protein by measuring the (13)C natural abundance in glycolate using natural or deuterated glycolate as a substrate. Our results suggest that several elemental steps were associated with an hydrogen/deuterium isotope effect and that glycolate α-deprotonation itself was only partially rate-limiting. Calculations of commitment factors from observed kinetic isotope effect values support a hydride transfer mechanism. No significant differences were seen between C3 and C4 enzymes.
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Affiliation(s)
- Younès Dellero
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Caroline Mauve
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France, Plateforme Métabolisme-Métabolome, Saclay Plant Sciences, Institut de Biologie des Plantes, Bâtiment 630, 91405 Orsay Cedex, France, and
| | - Edouard Boex-Fontvieille
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Valérie Flesch
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Mathieu Jossier
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Guillaume Tcherkez
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France, Plateforme Métabolisme-Métabolome, Saclay Plant Sciences, Institut de Biologie des Plantes, Bâtiment 630, 91405 Orsay Cedex, France, and Institut Universitaire de France, 103 Boulevard Saint-Michel, 75005 Paris, France
| | - Michael Hodges
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France,
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Daka JL, Achilonu I, Dirr HW. The isomerization of Δ5-androstene-3,17-dione by the human glutathione transferase A3-3 proceeds via a conjugated heteroannular diene intermediate. J Biol Chem 2014; 289:32243-32252. [PMID: 25248748 PMCID: PMC4231698 DOI: 10.1074/jbc.m114.601609] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Revised: 09/22/2014] [Indexed: 11/06/2022] Open
Abstract
The seemingly simple proton abstraction reactions underpin many chemical transformations, including isomerization reactions, and are thus of immense biological significance. Despite the energetic cost, enzyme-catalyzed proton abstraction reactions show remarkable rate enhancements. The pathways leading to these accelerated rates are numerous and on occasion partly enigmatic. The isomerization of the steroid Δ(5)-androstene-3,17-dione by the glutathione transferase A3-3 in mammals was investigated to gain insight into the mechanism. Particular emphasis was placed on the nature of the transition state, the intermediate suspected of aiding this process, and the hydrogen bonds postulated to be the stabilizing forces of these transient species. The UV-visible detection of the intermediate places this species in the catalytic pathway, whereas fluorescence spectroscopy is used to obtain the binding constant of the analog intermediate, equilenin. Solvent isotope exchange reveals that proton abstraction from the substrate to form the intermediate is rate-limiting. Analysis of the data in terms of the Marcus formalism indicates that the human glutathione transferase A3-3 lowers the intrinsic kinetic barrier by 3 kcal/mol. The results lead to the conclusion that this reaction proceeds through an enforced concerted mechanism in which the barrier to product formation is kinetically insignificant.
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Affiliation(s)
- Jonathan L Daka
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Ikechukwu Achilonu
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa
| | - Heini W Dirr
- Protein Structure-Function Research Unit, School of Molecular and Cell Biology, University of the Witwatersrand, Johannesburg 2050, South Africa.
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Hall J, Reschke S, Cao H, Leimkühler S, Hille R. The reductive half-reaction of xanthine dehydrogenase from Rhodobacter capsulatus: the role of Glu232 in catalysis. J Biol Chem 2014; 289:32121-32130. [PMID: 25258317 DOI: 10.1074/jbc.m114.603456] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The kinetic properties of an E232Q variant of the xanthine dehydrogenase from Rhodobacter capsulatus have been examined to ascertain whether Glu(232) in wild-type enzyme is protonated or unprotonated in the course of catalysis at neutral pH. We find that kred, the limiting rate constant for reduction at high [xanthine], is significantly compromised in the variant, a result that is inconsistent with Glu(232) being neutral in the active site of the wild-type enzyme. A comparison of the pH dependence of both kred and kred/Kd from reductive half-reaction experiments between wild-type and enzyme and the E232Q variant suggests that the ionized Glu(232) of wild-type enzyme plays an important role in catalysis by discriminating against the monoanionic form of substrate, effectively increasing the pKa of substrate by two pH units and ensuring that at physiological pH the neutral form of substrate predominates in the Michaelis complex. A kinetic isotope study of the wild-type R. capsulatus enzyme indicates that, as previously determined for the bovine and chicken enzymes, product release is principally rate-limiting in catalysis. The disparity in rate constants for the chemical step of the reaction and product release, however, is not as great in the bacterial enzyme as compared with the vertebrate forms. The results indicate that the bacterial and bovine enzymes catalyze the chemical step of the reaction to the same degree and that the faster turnover observed with the bacterial enzyme is due to a faster rate constant for product release than is seen with the vertebrate enzyme.
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Affiliation(s)
- James Hall
- Department of Biochemistry, University of California, Riverside, California 92521 and
| | - Stefan Reschke
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University Potsdam, 14476 Potsdam, Germany
| | - Hongnan Cao
- Department of Biochemistry, University of California, Riverside, California 92521 and
| | - Silke Leimkühler
- Department of Molecular Enzymology, Institute of Biochemistry and Biology, University Potsdam, 14476 Potsdam, Germany
| | - Russ Hille
- Department of Biochemistry, University of California, Riverside, California 92521 and.
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