title: Superoxide Dismutase Inhibition of Oxidation of Ubiquinol and Concomitant Formation of Hydrogen Peroxide.
abstract: We measured ubiquinone (CoQ0) and hydrogen peroxide (H2O2) formed in the process of oxidation of ubiquinol (CoQ0H2). We found that copper-zinc superoxide dismutase and manganese superoxide dismutase inhibited both the CoQ0 formation and the H2O2 formation only in the presence of chelators such as DTPA (diethylenetriaminepentaacetic acid). The amount of H2O2 was almost equal to that of CoQ0, indicating that the H2O2 formation was coupled with the CoQ0 formation. The lack of inhibitory effects of the corresponding heat-inactivated superoxide dismutase (SOD) confirmed that the inhibition by the original SOD was due to its enzymatic activity. We propose that CoQ0H2 oxidation occurs as a chain reaction with superoxide as the chain carrier and that SOD inhibits this reaction by lowering the superoxide concentration.
authors.affiliation: a School of Food and Nutritional Sciences, University of Shizuoka 52-1 Yada , Shizuoka 422 , Japan.
authors.forename: T
authors.initials: T
authors.lastname: Nakayama
authors.affiliation: a School of Food and Nutritional Sciences, University of Shizuoka 52-1 Yada , Shizuoka 422 , Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hashimoto
authors.affiliation: a School of Food and Nutritional Sciences, University of Shizuoka 52-1 Yada , Shizuoka 422 , Japan.
authors.forename: K
authors.initials: K
authors.lastname: Hashimoto
keywords: hydrogen peroxide; superoxide; superoxide dismutase (SOD); ubiquinol; ubiquinone