Mechanistic Studies of Methane Biogenesis by Methyl-Coenzyme M Reductase: Evidence that Coenzyme B Participates in Cleaving the C−S Bond of Methyl-Coenzyme M
- 1 October 2001
- journal article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 40 (43), 12875-12885
- https://doi.org/10.1021/bi011196y
Abstract
Methyl-coenzyme M reductase (MCR), the key enzyme in methanogenesis, catalyzes methane formation from methyl-coenzyme M (methyl-SCoM) and N-7-mercaptoheptanoylthreonine phosphate (CoBSH). Steady-state and presteady-state kinetics have been used to test two mechanistic models that contrast in the role of CoBSH in the MCR-catalyzed reaction. In class 1 mechanisms, CoBSH is integrally involved in methane formation and in C−S (methyl-SCoM) bond cleavage. On the other hand, in class 2 mechanisms, methane is formed in the absence of CoBSH, which functions to regenerate active MCR after methane is released. Steady-state kinetic studies are most consistent with a ternary complex mechanism in which CoBSH binds before methane is formed, as found earlier [Bonacker et al. (1993) Eur. J. Biochem. 217, 587−595]. Presteady-state kinetic experiments at high MCR concentrations are complicated by the presence of tightly bound CoBSH in the purified enzyme. Chemical quench studies in which 14CH3-SCoM is rapidly reacted with active MCRred1 in the presence versus the absence of added CoBSH indicate that CoBSH is required for a single-turnover of methyl-SCoM to methane. Similar single turnover studies using a CoBSH analogue leads to the same conclusion. The results are consistent with class 1 mechanisms in which CoBSH is integrally involved in methane formation and in C−S (methyl-SCoM) bond cleavage and are inconsistent with class 2 mechanisms in which CoBSH binds after methane is formed. These are the first reported pre-steady-state kinetic studies of MCR.Keywords
This publication has 18 references indexed in Scilit:
- Cryoreduction of Methyl-Coenzyme M Reductase: EPR Characterization of Forms, MCRox1 and MCRred1Journal of the American Chemical Society, 2001
- On the mechanism of biological methane formation: structural evidence for conformational changes in methyl-coenzyme M reductase upon substrate bindingJournal of Molecular Biology, 2001
- On the Assignment of Nickel Oxidation States of the Ox1, Ox2 Forms of Methyl−Coenzyme M ReductaseJournal of the American Chemical Society, 1999
- Purified Methyl‐Coenzyme‐M Reductase is Activated when the Enzyme‐Bound Coenzyme F430 is Reduced to the Nickel(I) Oxidation State by Titanium(III) CitrateEuropean Journal of Biochemistry, 1997
- Properties of the two isoenzymes of methyl‐coenzyme M reductase in Methanobacterium thermoautotrophicumEuropean Journal of Biochemistry, 1993
- Methyl‐coenzyme M reductase preparations with high specific activity from H2‐preincubated cells of Methanobacterium thermoautotrophicumFEBS Letters, 1991
- Methanobacterium thermoautotrophicum contains a soluble enzyme system that specifically catalyzes the reduction of the heterodisulfide of coenzyme M and 7‐mercaptoheptanoylthreonine phosphate with H2FEBS Letters, 1988
- On the role of N‐7‐mercaptoheptanoyl‐O‐phospho‐L‐threonine (component B) in the enzymatic reduction of methyl‐coenzyme M to methaneFEBS Letters, 1987
- Biosynthetic evidence for a nickel tetrapyrrole structure of factor F430 from Methanobacterium thermoautotrophicumFEBS Letters, 1980
- Growth parameters (K s, ?max, Y s) of Methanobacterium thermoautotrophicumArchiv für Mikrobiologie, 1980