IUBMB Enzyme Nomenclature


Accepted name: sirohydrochlorin ferrochelatase

Reaction: siroheme + 2 H+ = sirohydrochlorin + Fe2+

For diagram click here.

Other name(s): CysG; Met8P; SirB; sirohydrochlorin ferro-lyase (incorrect)

Systematic name: siroheme ferro-lyase (sirohydrochlorin-forming)

Comments: This enzyme catalyses the third of three steps leading to the formation of siroheme from uroporphyrinogen III. The first step involves the donation of two S-adenosyl-L-methionine-derived methyl groups to carbons 2 and 7 of uroporphyrinogen III to form precorrin-2 (EC, uroporphyrin-III C-methyltransferase) and the second step involves an NAD+-dependent dehydrogenation to form sirohydrochlorin from precorrin-2 (EC, precorrin-2 dehydrogenase). In Saccharomyces cerevisiae, the last two steps are carried out by a single bifunctional enzyme, Met8p. In some bacteria, steps 1-3 are catalysed by a single multifunctional protein called CysG, whereas in Bacillus megaterium, three separate enzymes carry out each of the steps, with SirB being responsible for the above reaction.

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


1. Schubert, H.L., Raux, E., Brindley, A.A., Leech, H.K., Wilson, K.S., Hill, C.P. and Warren, M.J. The structure of Saccharomyces cerevisiae Met8p, a bifunctional dehydrogenase and ferrochelatase. EMBO J. 21 (2002) 2068-2075. [PMID: 11980703]

2. Warren, M.J., Raux, E., Schubert, H.L. and Escalante-Semerena, J.C. The biosynthesis of adenosylcobalamin (vitamin B12). Nat. Prod. Rep. 19 (2002) 390-412. [PMID: 12195810]

[EC created 2004]

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