Mitochondrial production of hydrogen peroxide in Saccharomyces cerevisiae.

Intact mitochondria isolated from bakers' yeast and showing respiratory control by ADP, released H2O2 to the suspending medium at rates of 1.2.2.2 nmol/min per mg of protein depending on the mitochondrial metabolic condition. Release of H2O2 from mitochondria increased 1.3 times in swollen mitochondria and 1.2 times after osmotic shock, i.e., when the outer membrane was damaged. Under physiological conditions, yeast cytochrome c peroxidase, mainly located in the intermembrane space, utilized about 53-55% of the H2O2 generated by the respiratory chain at the inner membrane, partially preventing H2O2 diffusion to the cytosol. Apparently, the outer mitochondrial membrane was highly permeable to H2O2. It is claimed that the risk of cell injury due to H2O2, O-2 and HO is slightly higher in the stationary phase than in the logarithmic phase of growth.