Zusammenfassung
Cytochrome c oxidase (EC 1.9.3.1), the oxygen-reducing member of the respiratory chains of mitochondria and several aerobic bacteria, catalyzes flux of reducing equivalents to the highly oxidizing O2-H2O couple and conserves energy as a proton-motive force. These enzymes are members of a large family of related heme-copper oxidases; others are the hydroquinone oxidases, of which cytochrome bo 3 of Escherichia coli is the best characterized. Apart from the intriguing catalysis of O2 reduction to water, this class of enzymes conserves energy by vectorial functioning as proton and electrical charge trans locators. This leads to primary conservation of respiratory redox energy as an electrochemical proton gradient across the mitochondrial or bacterial membrane, which is secondarily utilized as the driving force for the oxidative synthesis of ATP (Mitchell, 1966). Before the elucidation of the crystal structures of cytochrome c oxidase from Paracoccus denitrificans (Iwata et al., 1995) and bovine heart mitochondria (Tsukihara et al., 1995, 1996), the heme-copper oxidases have been the subject of many review articles, which have highlighted their functional (Malmström, 1990a,b; Cooper, 1990; Chan and Li, 1990; Wilson and Bickar, 1991; Rich, 1991; Babcock and Wikström, 1992), structural (Capaldi, 1990; Saraste, 1990; Saraste et al., 1991; Gennis, 1992; Haltia and Wikström, 1992; Hosler et al., 1993), and evolutionary aspects (Kadenbach et al., 1987, 1991; Castresana et al., 1995; Saraste et al., 1996). The present account is not intended as a review.
