Cellular Senescence in Yeast Caused by Carbon-Source Starvation

I. Changes in Activities of Respiratory System and Lipid Peroxidation Activity

Abstract

Cells of Saccharomyces cerevisiae survived for 14 days after the cessation of growth caused by the consumption of lactate, and they began to die exponentially. In the long lasting stationary phase, respiratory activity of yeast cells decreased stepwise: the first step occurred while cells were still viable and the second step almost concomitantly with the loss of viability. The inactivations of respiratory enzymes, such as succinate-cytochrome c reductase system and cytochrome oxidase [EC 1. 9. 3. 1], started between the two impairment steps of respiration.
The involvement of lipid peroxidation reaction in the first-step decrease in respiratory activity is suggested. The activity of this reaction, which required the presence of NADPH, increased markedly from the late log phase to the early stationary phase. In vitro experiments showed that succinate oxidase activity of yeast mitochondria was partially inactivated by lipid peroxidation system extracted from yeast.