IUBMB Enzyme Nomenclature


Accepted name: [methyl-Co(III) quaternary-amine-specific corrinoid protein]—tetrahydrofolate methyltransferase

Reaction: [a methyl-Co(III) quaternary-amine-specific corrinoid protein] + tetrahydrofolate = N5-methyltetrahydrofolate + a [Co(I) quaternary-amine-specific corrinoid protein]

Other name(s): mtqA (gene name) (ambiguous); [methyl-Co(III) MtqC corrinoid protein]—tetrahydrofolate methyltransferase

Systematic name: [methylated quaternary-amine-specific corrinoid protein]:tetrahydrofolate methyltransferase

Comments: The enzyme, characterized from the acetogenic gut bacterium Eubacterium limosum, participates in a pathway for the degradation of some quaternary amine compounds (L-proline betaine and L-carnitine). The enzyme catalyses the transfer of a methyl group bound to the cobalt cofactor of a dedicated corrinoid protein (bacterial MtqC) to tetrahydrofolate. 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. Picking, J.W., Behrman, E.J., Zhang, L. and Krzycki, J.A. MtpB, a member of the MttB superfamily from the human intestinal acetogen Eubacterium limosum, catalyzes proline betaine demethylation. J. Biol. Chem. 294 (2019) 13697-13707. [PMID: 31341018]

2. 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 2023]

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