Involvement of glutathione transferases, Gtt1and Gtt2, with oxidative stress response generated by H₂O₂ during growth of Saccharomyces cerevisiae

Abstract

Glutathione transferases are detoxifying enzymes responsible for eliminating toxic compounds generated under a variety of stress conditions. Saccharomyces cerevisiae control cells and glutathione transferase mutant strains (gtt1 and gtt2) were used to analyze tolerance, lipid and protein oxidation as oxidative stress markers during growth in the presence of H₂O₂. Glucose 6-phosphate dehydrogenase (G6PD) and glutathione reductase were assayed to monitor the capacity of cells to recycle glutathione. Although a reduction in growth was observed, deletion of GTT1 showed less inhibition by H₂O₂ than the control strain. Cells showed a significant reduction in cellular viability during the first hours of growth, the gtt1 mutant being hypersensitive even after 24 h of H₂O₂ exposure. As a consequence of oxidative stress caused by exposure to H₂O₂, an increase in lipid peroxidation was observed, mainly in the glutathione transferase mutant strains. While protein carbonylation increased by 17% and 23%, respectively, after 2 h in the presence of H₂O₂ in the control and gtt2 mutant, a 40% increase was observed in the gtt1 strain after 24-h exposure. The antioxidant G6PD and glutathione reductase activities were affected in the gtt1 mutant during H₂O₂ exposure, which could be critical for recycling glutathione. The same was observed for the gtt2 mutant after 2-h treatment, indicating that glutathione recycling might be associated with the detoxification process. Thus, glutathione transferases, Gtt1 and Gtt2, seem to be crucial in the response to H₂O₂ stress.

Keywords:

• HYDROGEN PEROXIDE
• GLUTATHIONE TRANSFERASES
• OXIDATIVE DAMAGE
• SACCHAROMYCES CEREVISIAE