IUBMB Enzyme Nomenclature


Accepted name: superoxide oxidase

Reaction: 2 O2 + ubiquinol = 2 superoxide + ubiquinone + 2 H+

Other name(s): SOO; CybB; cytochrome b561; superoxide:ubiquinone oxidoreductase

Systematic name: ubiquinol:oxygen oxidoreductase (superoxide-forming)

Comments: This membrane-bound, di-heme containing enzyme, identified in the bacterium Escherichia coli, is responsible for the detoxification of superoxide in the periplasm. In vivo the reaction proceeds in the opposite direction of that shown and produces oxygen. Superoxide production was only observed when the enzyme was incubated in vitro with an excess of ubiquinol.

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


1. Murakami, H., Kita, K. and Anraku, Y. Cloning of cybB, the gene for cytochrome b561 of Escherichia coli K12. Mol. Gen. Genet. 198 (1984) 1-6. [PMID: 6097799]

2. Murakami, H., Kita, K. and Anraku, Y. Purification and properties of a diheme cytochrome b561 of the Escherichia coli respiratory chain. J. Biol. Chem 261 (1986) 548-551. [PMID: 3510204]

3. Lundgren, C.AK., Sjostrand, D., Biner, O., Bennett, M., Rudling, A., Johansson, A.L., Brzezinski, P., Carlsson, J., von Ballmoos, C. and Hogbom, M. Scavenging of superoxide by a membrane-bound superoxide oxidase. Nat. Chem. Biol. 14 (2018) 788-793. [PMID: 29915379]

[EC created 2019]

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