Glutathione peroxidase induction protects Saccharomyces cerevisiae sod1 Δsod2Δ double mutants against oxidative damage

Abstract

Saccharomyces cerevisiae mutants deficient in superoxide dismutase genes (sod1Δ, sod2Δ and the double mutant) were subjected to H2O2 stress in the stationary phase. The highest sensitivity was observed in the sod2Δ mutant, while the sod1Δsod2Δ double mutant was not sensitive. sod mutants had lower catalase activity (44%) than wildtype cells, independent of H2O2 stress. Untreated cells of sod1Δsod2Δ double mutants showed increased glutathione peroxidase activity (126%), while sod1Δ had lower activity (77%) than the wild type. Glutathione levels in sod1Δ were increased (200-260%) after exposure to various H2O2 concentrations. In addition, the highest malondialdehyde levels could be observed without H2O2 treatment in sod1Δ (167%) and sod2Δ (225%) mutants. In contrast, the level of malondialdehyde in the sod1Δsod2Δ double mutant was indistinguishable from that of the wild type. These results suggest that resistance to H2O2 by sod1Δsod2Δ 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 sod1Δ mutants.