Glutathione peroxidase induction protects Saccharomyces cerevisiae sod1deltasod2delta double mutants against oxidative damage

Saccharomyces cerevisiae mutants deficient in superoxide dismutase genes (sod1∆, sod2∆and the double mutant) were subjected to H2O2 stress in the stationary phase. The highest sensitivity was observed in the sod2∆mutant, while the sod1∆sod2∆double mutant was not sensitive. sod mutants had lower catalase activity (44%) than wildtype cells, independent of H2O2 stress. Untreated cells of sod1∆sod2∆ double mutants showed increased glutathione peroxidase activity (126%), while sod1∆had lower activity (77%) than the wild type. Glutathione levels in sod1∆were increased (200-260%) after exposure to various H2O2 concentrations. In addition, the highest malondialdehyde levels could be observed without H2O2 treatment in sod1∆ (167%) and sod2∆(225%) mutants. In contrast, the level of malondialdehyde in the sod1∆sod2∆double mutant was indistinguishable from that of the wild type. These results suggest that resistance to H2O2 by sod1∆sod2∆cells depends on the induction of glutathione peroxidase and is independent of catalase, and that glutathione is a primary antioxidant in the defense against H2O2 in stationary phase sod1∆ mutants