On the mechanism of methyl-coenzyme M reductase

Methyl-coenzyme M reductase (MCR) catalyzes the reaction of methyl-coenzyme M (CH3-SCoM) and coenzyme B (HS-CoB) to methane and the corresponding heterodisulfide CoM-S-S-CoB. This unique reaction proceeds under strictly anaerobic conditions in the presence of coenzyme F430, a Ni-porphinoid. MCR is a...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2005-11 (21), p.3451-3458
Main Author: Ermler, Ulrich
Format: Article
Language:English
Subjects:
Catalysis
Enzyme Inhibitors - chemistry
Enzyme Inhibitors - pharmacology
Kinetics
Metalloporphyrins - chemistry
Metalloporphyrins - metabolism
Oxidoreductases - antagonists & inhibitors
Oxidoreductases - chemistry
Oxidoreductases - metabolism
Substrate Specificity
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Summary:Methyl-coenzyme M reductase (MCR) catalyzes the reaction of methyl-coenzyme M (CH3-SCoM) and coenzyme B (HS-CoB) to methane and the corresponding heterodisulfide CoM-S-S-CoB. This unique reaction proceeds under strictly anaerobic conditions in the presence of coenzyme F430, a Ni-porphinoid. MCR is a large (alphabetagamma)2 heterohexameric protein complex containing two 50 A long active sites channels. Coenzyme F430 is embedded at the channel bottom and the substrates CH3-SCoM and HS-CoB bind in front of F430 into a solvent free and hydrophobic channel segment. Two principally different catalytic mechanisms are currently discussed. Mechanism I is based on a nucleophilic attack of Ni(I) onto the methyl group of CH3-SCoM yielding methyl-Ni(III) and mechanism II on an attack of Ni(I) onto the thioether sulfur of CH3-SCoM generating a Ni(II)-SCoM intermediate. Both mechanisms are discussed in the light of a large number of data collected about MCR over the last twenty years.
ISSN:1477-9226
1477-9234
DOI:10.1039/b506697b