Cytochrome oxidase-catalyzed superoxide generation from hydrogen peroxide.
Superoxide dismutase is shown to affect spectral changes observed upon cytochrome c oxidase reaction with H2O2, which indicates a possibility of O2- radicals being formed in the reaction. Using DMPO as a spin trap, generation of superoxide radicals from H2O2 in the presence of cytochrome oxidase is directly demonstrated. The process is inhibited by cyanide and is not observed with a heat-denatured enzyme pointing to a specific reaction in the oxygen-reducing centre of cytochrome c oxidase. The data support a hypothesis on a catalase cycle catalyzed by cytochrome c oxidase in the presence of excess H2O2 (Vygodina and Konstantinov (1988) Ann. NY Acad. Sci., 550, 124-138): (formula: see text)
Ksenzenko MYu
A.N. Belozersky Institute of Physico-Chemical Biology, Moscow State University, USSR.
Vygodina
T V
TV
Berka
V
V
Ruuge
E K
EK
Konstantinov
A A
AA
D000818:Animals; D002384:Catalysis; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000201:enzymology; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
D013481:Superoxides; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D003576:Electron Transport Complex IV