Mariani Diana, Mathias Cristiane J, da Silva Carmelita G, Herdeiro Ricardo da Silva, Pereira Ricardo, Panek Anita D, Eleutherio Elis C A, Pereira Marcos Dias
Departamento de Bioquímica, Instituto de Química, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Redox Rep. 2008;13(6):246-54. doi: 10.1179/135100008X309028.
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.
谷胱甘肽转移酶是负责清除在各种应激条件下产生的有毒化合物的解毒酶。酿酒酵母对照细胞和谷胱甘肽转移酶突变株（gtt1和gtt2）用于分析在过氧化氢存在下生长期间作为氧化应激标志物的耐受性、脂质和蛋白质氧化。测定了葡萄糖6-磷酸脱氢酶（G6PD）和谷胱甘肽还原酶，以监测细胞回收谷胱甘肽的能力。虽然观察到生长有所下降，但与对照菌株相比，GTT1的缺失显示出对过氧化氢的抑制作用较小。细胞在生长的最初几个小时内细胞活力显著降低，即使在暴露于过氧化氢24小时后，gtt1突变体仍表现出超敏反应。由于暴露于过氧化氢引起的氧化应激，观察到脂质过氧化增加，主要在谷胱甘肽转移酶突变株中。在对照和gtt2突变体中，在过氧化氢存在2小时后，蛋白质羰基化分别增加了17%和23%，而在gtt1菌株中，暴露24小时后增加了40%。在过氧化氢暴露期间，gtt1突变体中的抗氧化剂G6PD和谷胱甘肽还原酶活性受到影响，这可能对谷胱甘肽的回收至关重要。在处理2小时后，gtt2突变体也观察到同样的情况，表明谷胱甘肽回收可能与解毒过程有关。因此，谷胱甘肽转移酶Gtt1和Gtt2似乎在对过氧化氢应激的反应中至关重要。
