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Coenzyme M is a coenzyme required for methyl-transfer reactions in the metabolism of methanogens. The coenzyme is an anion with the formula HSCH
2CH
2SO−
3. It is named 2-mercaptoethanesulfonate and abbreviated HS–CoM. The cation is unimportant, but the sodium salt is most available. Mercaptoethanesulfonate contains both a thiol, which is the main site of reactivity, and a sulfonate group, which confers solubility in aqueous media.
Biochemical role
The coenzyme is the C1 donor in methanogenesis. It is converted to methyl-coenzyme M thioether, the thioether CH
3SCH
2CH
2SO−
3, in the penultimate step to methane formation. Methyl-coenzyme M reacts with coenzyme B, 7-thioheptanoylthreoninephosphate, to give a heterodisulfide, releasing methane:
3–S–CoM + HS–CoB → CH
4 + CoB–S–S–CoM
This induction is catalyzed by the enzyme methyl-coenzyme M reductase, which restricts cofactor F430 as the prosthetic group.