Cytochrome Oxidase and Peroxide Metabolism
Hydrogen peroxide accelerated the cytochrome oxidase-catalyzed oxidation of ferrocytochrome c whereas in the Polarographic assay it depressed the oxygen consumption even though the extent was small. Calculations based on parallel determination of both cytochrome c oxidase and peroxidase activities revealed that 8–10% of the total electron flux was directed to the peroxide when nearly equal oxidizing equivalents of both oxidants were present in the reaction system. The depressed oxygen uptake suggests that hydrogen peroxide acts as an electron acceptor by drawing a portion of the electron flux which otherwise is directed to molecular oxygen. On the contrary, the accelerated oxidation of ferrocytochrome c suggests that the total electron flux through cytochrome oxidase increases possibly by activation of a reserve capacity of the enzyme to utilize hydrogen peroxide in addition to oxygen. The acceleration effect became pronounced as the oxygen concentration was lowered to 1.5–2.1 μM.
KeywordsElectron Acceptor Cytochrome Oxidase Versus Versus Versus Electron Flux Reduction Level
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