IUBMB Enzyme Nomenclature


Accepted name: L-carnitine—corrinoid protein Co-methyltransferase

Reaction: L-carnitine + a [Co(I) quaternary-amine-specifc corrinoid protein] = a [methyl-Co(III) quaternary-amine-specific corrinoid protein] + L-norcarnitine

Glossary: L-norcarnitine = (3R)-4-(dimethylamino)-3-hydroxybutanoate

Other name(s): mtcB (gene name)

Systematic name: L-carnitine:[Co(I) quaternary-amine-specifc corrinoid protein] Co-methyltransferase

Comments: The enzyme, characterized from the bacterium Eubacterium limosum, is a component of a system that transfers a methyl group from L-carnitine to tetrahydrofolate, as part of an L-carnitine degradation pathway. The resulting 5-methyltetrahydrofolate is processed to acetyl-CoA via the Wood—Ljungdahl pathway.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Kountz, D.J., Behrman, E.J., Zhang, L. and Krzycki, J.A. MtcB, a member of the MttB superfamily from the human gut acetogen Eubacterium limosum, is a cobalamin-dependent carnitine demethylase. J. Biol. Chem. 295 (2020) 11971-11981. [PMID: 32571881]

[EC created 2021]

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