Reaction: 4 ferrocytochrome c + O2 + 4 H+ = 4 ferricytochrome c + 2 H2O
Other name(s): cytochrome aa3; cytochrome caa3; cytochrome bb3; cytochrome cbb3; cytochrome ba3; cytochrome a3; Warburg’s respiratory enzyme; indophenol oxidase; indophenolase; complex IV (mitochondrial electron transport); ferrocytochrome c oxidase; cytochrome oxidase (ambiguous); NADH cytochrome c oxidase (incorrect)
Systematic name: ferrocytochrome-c:oxygen oxidoreductase
Comments: An oligomeric membrane heme-Cu: O2 reductase-type enzyme that terminates the respiratory chains of aerobic and facultative aerobic organisms. The reduction of O2 to water is accompanied by the extrusion of four protons. The cytochrome-aa3 enzymes of mitochondria and many bacterial species are the most abundant group, but other variations, such as the bacterial cytochrome-cbb3 enzymes, also exist. All of the variants have a conserved catalytic core subunit (subunit I) that contains a low-spin heme (of a- or b-type), a binuclear metal centre composed of a high-spin heme iron (of a-, o-, or b-type heme, referred to as a3, o3 or b3 heme), and a Cu atom (CuB). Besides subunit I, the enzyme usually has at least two other core subunits: subunit II is the primary electron acceptor; subunit III usually does not contain any cofactors, but in the case of cbb3-type enzymes it is a diheme c-type cytochrome. While most bacterial enzymes consist of only 3-4 subunits, the mitochondrial enzyme is much more complex and contains 14 subunits.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
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