IUBMB Enzyme Nomenclature


Accepted name: cobalt-factor III methyltransferase

Reaction: S-adenosyl-L-methionine + cobalt-factor III + reduced acceptor = S-adenosyl-L-homocysteine + cobalt-precorrin-4 + acceptor

For diagram of reaction click here.

Other name(s): CbiH60 (gene name)

Systematic name: S-adenosyl-L-methionine:cobalt-factor III 17-methyltransferase (ring contracting)

Comments: Isolated from the bacterium Bacillus megaterium. The enzyme, which participates in the anaerobic (early cobalt insertion) pathway of adenosylcobalamin biosynthesis, catalyses a crucial reaction where the tetrapyrrole ring contracts as a result of methylation of C-17. Contains a [4Fe-4S] cluster. It can also convert cobalt-precorrin-3 to cobalt-precorrin-4. The reductant may be thioredoxin. See EC, precorrin-3B C17-methyltransferase, for the corresponding enzyme that participates in the aerobic cobalamin biosynthesis pathway.

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


1. Moore, S.J., Biedendieck, R., Lawrence, A.D., Deery, E., Howard, M.J., Rigby, S.E. and Warren, M.J. Characterization of the enzyme CbiH60 involved in anaerobic ring contraction of the cobalamin (vitamin B12) biosynthetic pathway. J. Biol. Chem. 288 (2013) 297-305. [PMID: 23155054]

[EC created 2013]

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