IUBMB Enzyme Nomenclature


Accepted name: heme oxygenase (biliverdin-producing)

Reaction: protoheme + 3 [reduced NADPH—hemoprotein reductase] + 3 O2 = biliverdin + Fe2+ + CO + 3 [oxidized NADPH—hemoprotein reductase] + 3 H2O

For diagram of reaction click here and mechanism (click here)
Other name(s): ORP33 proteins; haem oxygenase (ambiguous); heme oxygenase (decyclizing) (ambiguous); heme oxidase (ambiguous); haem oxidase (ambiguous); heme oxygenase (ambiguous); heme,hydrogen-donor:oxygen oxidoreductase (α-methene-oxidizing, hydroxylating)

Systematic name: protoheme,NADPH—hemoprotein reductase:oxygen oxidoreductase (α-methene-oxidizing, hydroxylating)

Comments: This mammalian enzyme participates in the degradation of heme. The terminal oxygen atoms that are incorporated into the carbonyl groups of pyrrole rings A and B of biliverdin are derived from two separate oxygen molecules [4]. The third oxygen molecule provides the oxygen atom that converts the α-carbon to CO. The enzyme requires NAD(P)H and EC, NADPH—hemoprotein reductase. cf. EC, heme oxygenase (biliverdin-producing, ferredoxin).

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9059-22-7


1. Maines, M.D., Ibrahim, N.G. and Kappas, K. Solubilization and partial purification of heme oxygenase from rat liver. J. Biol. Chem. 252 (1977) 5900-5903. [PMID: 18477]

2. Sunderman, F.W., Jr., Downs, J.R., Reid, M.C. and Bibeau, L.M. Gas-chromatographic assay for heme oxygenase activity. Clin. Chem. 28 (1982) 2026-2032. [PMID: 6897023]

3. Yoshida, T., Takahashi, S. and Kikuchi, J. Partial purification and reconstitution of the heme oxygenase system from pig spleen microsomes. J. Biochem. (Tokyo) 75 (1974) 1187-1191. [PMID: 4370250]

4. Noguchi, M., Yoshida, T. and Kikuchi, G. Specific requirement of NADPH-cytochrome c reductase for the microsomal heme oxygenase reaction yielding biliverdin IX α. FEBS Lett. 98 (1979) 281-284. [PMID: 105935]

5. Lad, L., Schuller, D.J., Shimizu, H., Friedman, J., Li, H., Ortiz de Montellano, P.R. and Poulos, T.L. Comparison of the heme-free and-bound crystal structures of human heme oxygenase-1. J. Biol. Chem. 278 (2003) 7834-7843. [PMID: 12500973]

[EC created 1972 as EC, modified 2006, transferred 2015 to EC, modified 2016]

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