cytochrome-c oxidase activity cytochrome oxidase activity Reactome:REACT_113736 NADH cytochrome c oxidase ferrocytochrome-c:oxygen oxidoreductase Catalysis of the reaction: 4 ferrocytochrome c + O2 + 4 H+ = 4 ferricytochrome c + 2 H2O. Reactome:REACT_113311 Reactome:REACT_113276 warburg's respiratory enzyme activity MetaCyc:CYTOCHROME-C-OXIDASE-RXN cytochrome c oxidase activity indophenolase ferrocytochrome c oxidase EC:1.9.3.1 indophenol oxidase Reactome:REACT_99789 cbb3-type cytochrome c oxidase ba3-type cytochrome c oxidase Reactome:REACT_115027 cytochrome a3 activity Reactome:REACT_6149 The reduction of O2 to water is accompanied by the extrusion of four protons from the intramitochondrial compartment. GO:0004129 Reactome:REACT_78871 caa3-type cytochrome c oxidase aa3-type cytochrome c oxidase Reactome:REACT_33608 complex IV (mitochondrial electron transport) activity molecular_function cytochrome aa3 activity heme-copper terminal oxidase activity hydrogen ion transmembrane transporter activity oxidoreductase activity, acting on a heme group of donors, oxygen as acceptor