title: Redox state of peroxy and ferryl intermediates in cytochrome c oxidase catalysis.
abstract: The redox states of the "peroxy" (P) and "ferryl" (F) intermediates formed during reoxidation of reduced bovine cytochrome c oxidase have been probed by reduction with both ferrocytochrome c and acetylpyridine NADH under anaerobic conditions using optical spectroscopy. The reduction of the P and F forms revealed that both are in very similar redox states. One-electron reduction of either the P or F form yields an optical spectrum primarily due to oxidized enzyme implying that the heme iron of cytochrome a3 is in the ferryl state in both forms. The F and P forms were found to be 1 and less than 1.3 oxidizing equiv, respectively, above the oxidized enzyme. The slightly higher oxidation state in the P form is interpreted as being due to an optically undetectable redox center presumably located in the binuclear cavity.
mesh_terms: D002384:Catalysis; D003574:Cytochrome c Group / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism*; D009249:NADP / Q000031:analogs & derivatives / Q000378:metabolism; D010084:Oxidation-Reduction; D013057:Spectrum Analysis; D013379:Substrate Specificity