Electron transport chain of Saccharomyces cerevisiae mitochondria is inhibited by H_2O_2 at succinate-cytochrome c oxidoreductase level without lipid peroxidation involvement

摘要

The deleterious effects of H_2O_2 on the electron transport chain of yeast mitochondria and on mitochondrial lipid peroxidation were evaluated. Exposure to H_2O_2 resulted in inhibition of the oxygen consumption in the uncoupled and phosphorylating states to 69% and 65%, respectively. The effect of H_2O_2 on the respiratory rate was associated with an inhibition of succinate-ubiquinone and succinate-DCIP oxidoreductase activities. Inhibitory effect of H_2O_2 on respiratory complexes was almost completely recovered by beta-mercaptoethanol treatment. H_2O_2 treatment resulted in full resistance to Qo site inhibitor myxothiazol and thus it is suggested that the quinol oxidase site (Qo) of complex III is the target for H_2O_2. H_2O_2 did not modify basal levels of lipid peroxidation in yeast mitochondria. However, H_2O_2 addition to rat brain and liver mitochondria induced an increase in lipid peroxidation. These results are discussed in terms of the known physiological differences between mammalian and yeast mitochondria.