IUBMB Enzyme Nomenclature


Accepted name: heme oxygenase (staphylobilin-producing)

Reaction: (1) protoheme + 5 reduced acceptor + 4 O2 = 5-oxo-δ-bilirubin + Fe2+ + formaldehyde + 5 acceptor + 4 H2O
(2) protoheme + 5 reduced acceptor + 4 O2 = 15-oxo-β-bilirubin + Fe2+ + formaldehyde + 5 acceptor + 4 H2O

EC heme oxygenase (staphylobilin-producing)
Glossary: β-staphylobilins = 10-oxo-δ-bilirubin = 3,7-bis(2-carboxyethyl)-2,8,13,18-tetramethyl-12,17-divinylbiladiene-ac-1,10,19(21H,24H)-trione
δ-staphylobilin = 10-oxo-δ-bilirubin = 3,7-bis(2-carboxyethyl)-2,8,12,17-tetramethyl-13,18-divinylbiladiene-ac-1,10,19(21H,24H)-trione

Other name(s): haem oxygenase (ambiguous); heme oxygenase (decyclizing) (ambiguous); heme oxidase (ambiguous); haem oxidase (ambiguous); heme oxygenase (ambiguous); isdG (gene name); isdI (gene name)

Systematic name: protoheme,hydrogen-donor:oxygen oxidoreductase (δ/β-methene-oxidizing, hydroxylating)

Comments: This enzyme, which is found in some pathogenic bacteria, is involved in an iron acquisition system that catabolizes the host's hemoglobin. The two enzymes from the bacterium Staphylococcus aureus, encoded by the isdG and isdI genes, produce 67.5 % and 56.2 % δ-staphylobilin, respectively.

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


1. Reniere, M.L., Ukpabi, G.N., Harry, S.R., Stec, D.F., Krull, R., Wright, D.W., Bachmann, B.O., Murphy, M.E. and Skaar, E.P. The IsdG-family of haem oxygenases degrades haem to a novel chromophore. Mol. Microbiol. 75 (2010) 1529-1538. [PMID: 20180905]

2. Matsui, T., Nambu, S., Ono, Y., Goulding, C.W., Tsumoto, K. and Ikeda-Saito, M. Heme degradation by Staphylococcus aureus IsdG and IsdI liberates formaldehyde rather than carbon monoxide. Biochemistry 52 (2013) 3025-3027. [PMID: 23600533]

[EC created 2013, modified 2017]

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