EC Explorer

7.1.1.9

cytochrome-c oxidase

4 ferrocytochrome c + O₂ + 8 H⁺_{[side 1]} = 4 ferricytochrome c + 2 H₂O + 4 H⁺_{[side 2]}

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)

ferrocytochrome-c:oxygen oxidoreductase

9001-16-5

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.

created 1961 as EC 1.9.3.1, modified 2000, transferred 2019 to EC 7.1.1.9, modified 2021