cytochrome-c oxidase

cy·to·chrome-c ox·i·dase (siґto-krōm okґsĭ-dās) [EC 1.9.3.1] an enzyme complex of the inner mitochondrial membrane that catalyzes the transfer of electrons from cytochrome c> to oxygen, oxidizing the former and reducing the latter in the final step of the electron transport chain (q.v.) by which oxygen is used for fuel combustion. The enzyme contains cytochromes a and a₃ and two copper atoms and is associated with proton translocation and the resultant synthesis of ATP. The Fe²⁺ in heme a has a strong affinity for CO; in the Fe³⁺ state it binds CN⁻, S²⁻, and N₃. The binding of these compounds inactivates the enzyme, a cause of their extreme toxicity for all aerobic organisms. Called also cytochrome aa_3> and cytochrome oxidase.