Costa V, Reis E, Quintanilha A, Moradas-Ferreira P
Departamento de Biologia Molecular, Instituto de Ciências Biomédicas de Abel Salazar, Porto, Portugal.
Arch Biochem Biophys. 1993 Feb 1;300(2):608-14. doi: 10.1006/abbi.1993.1084.
Saccharomyces cerevisiae aBR10 cells are able to develop resistance to lethal ethanol concentrations (14%, v/v), by preexposure to a sublethal heat shock (37 degrees C) or ethanol stress (8%, v/v). Heat shock and 8% ethanol stress had no effect on the concentrations of glutathione [reduced (GSH) and oxidized (GSSG) forms] and on glutathione reductase and CuZn superoxide dismutase (SOD) activities, suggesting that the development of resistance to lethal ethanol concentrations is independent of these antioxidant defenses. In fact, a S. cerevisiae mutant, deficient in CuZnSOD, had an even higher ethanol tolerance, compared to the wild-type strain, and this mutation did not impair a further acquisition of ethanol tolerance. In contrast to CuZnSOD, the MnSOD activity seems to play a more important role in ethanol resistance. The MnSOD activity of the S. cerevisiae aBR10 cells increased upon exposure to heat shock or 8% ethanol. The higher tolerance to 14% ethanol in CuZnSOD deficient cells was also associated to a higher MnSOD activity, as compared to the aBR10 cells; this activity decreased during both stress pretreatments (while still higher than that observed in the wild-type strain). The results obtained suggest that maximum ethanol tolerance is attained with a MnSOD activity close to 1.0 U/mg protein. On either side of this value, the increased sensitivity of S. cerevisiae cells to 14% ethanol might be due to an inability to prevent either superoxide radical- or hydrogen peroxide-induced damages, respectively. These results are supported by the fact that a MnSOD deficiency renders yeast cells more ethanol sensitive.
酿酒酵母aBR10细胞通过预先暴露于亚致死热休克（37℃）或乙醇胁迫（8%，v/v），能够对致死浓度的乙醇（14%，v/v）产生抗性。热休克和8%乙醇胁迫对谷胱甘肽[还原型（GSH）和氧化型（GSSG）形式]的浓度以及谷胱甘肽还原酶和铜锌超氧化物歧化酶（SOD）的活性没有影响，这表明对致死浓度乙醇的抗性发展与这些抗氧化防御机制无关。事实上，与野生型菌株相比，缺乏铜锌超氧化物歧化酶的酿酒酵母突变体具有更高的乙醇耐受性，并且这种突变不会损害其对乙醇耐受性的进一步获得。与铜锌超氧化物歧化酶不同，锰超氧化物歧化酶活性似乎在乙醇抗性中发挥更重要的作用。酿酒酵母aBR10细胞暴露于热休克或8%乙醇后，锰超氧化物歧化酶活性增加。与aBR10细胞相比，铜锌超氧化物歧化酶缺陷细胞对14%乙醇的更高耐受性也与更高的锰超氧化物歧化酶活性有关；在两种胁迫预处理期间，这种活性均下降（但仍高于野生型菌株中观察到的活性）。所获得的结果表明，当锰超氧化物歧化酶活性接近1.0 U/mg蛋白质时，可达到最大乙醇耐受性。在该值的两侧，酿酒酵母细胞对14%乙醇敏感性增加可能分别是由于无法预防超氧自由基或过氧化氢诱导损伤所致。锰超氧化物歧化酶缺陷使酵母细胞对乙醇更敏感这一事实支持了这些结果。
