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Issue 21, 2005
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On the mechanism of methyl-coenzyme M reductase

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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 (αβγ)2 heterohexameric protein complex containing two 50 Å 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.

Graphical abstract: On the mechanism of methyl-coenzyme M reductase

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Article information

12 May 2005
13 Jun 2005
First published
13 Sep 2005

Dalton Trans., 2005, 3451-3458
Article type

On the mechanism of methyl-coenzyme M reductase

U. Ermler, Dalton Trans., 2005, 3451
DOI: 10.1039/B506697B

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