IUBMB Enzyme Nomenclature


Accepted name: cobalt-precorrin 5A hydrolase

Reaction: cobalt-precorrin-5A + H2O = cobalt-precorrin-5B + acetaldehyde + 2 H+

For diagram click here.

Other name(s): CbiG (gene name)

Systematic name: obalt-precorrin 5A acylhydrolase

Comments: This enzyme hydrolyses the ring A acetate δ-lactone of cobalt-precorrin-5A resulting in the loss of the C-20 carbon and its attached methyl group in the form of acetaldehyde. This is a key reaction in the contraction of the porphyrin-type tetrapyrrole ring and its conversion to a corrin ring in the anaerobic (early cobalt insertion) adenosylcobalamin biosynthesis pathway.

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


1. Kajiwara, Y., Santander, P.J., Roessner, C.A., Perez, L.M. and Scott, A.I. Genetically engineered synthesis and structural characterization of cobalt-precorrin 5A and -5B, two new intermediates on the anaerobic pathway to vitamin B12: definition of the roles of the CbiF and CbiG enzymes. J. Am. Chem. Soc. 128 (2006) 9971-9978. [PMID: 16866557]

[EC created 2010]

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