title: Reduced cytochrome c oxidase. A new form absorbing at 443 and 603 nm.
abstract: Reduced cytochrome c oxidase is known to absorb strongly at 445 nm and 605 nm regardless of the chemical or physiological nature of the reductant. When the reduced oxidase is allowed to interact with cytochrome c3 under conditions in which there is no net change in the oxidation state of the oxidase, the absorption bands shift from those commonly found to 443 nm and 603 nm. This new oxidase form is postulated to be the intermediate in the catalytic cycle of the oxidase that results in the formation of the 418-nm form of the oxidized oxidase; it is further postulated that the 445-nm form is the intermediate in the catalytic cycle that results in the 428-nm form of the oxidized oxidase. The relevance of the 443-nm, 603-nm form to the conformational cycle of the oxidase as well as its possible involvement in energy transduction at Site II of oxidative phosphorylation are discussed.
mesh_terms: D000693:Anaerobiosis; D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism; D007700:Kinetics; D009206:Myocardium / Q000201:enzymology; D010084:Oxidation-Reduction; D013053:Spectrophotometry
chemical_list: D003576:Electron Transport Complex IV