Izawa S, Inoue Y, Kimura A
Laboratory of Molecular Breeding of Microorganisms, Kyoto University, Japan.
Biochem J. 1996 Nov 15;320 ( Pt 1)(Pt 1):61-7. doi: 10.1042/bj3200061.
Controversy about the importance of catalase in the detoxification of H2O2 in human erythrocytes continues. It has been suggested that catalase has no role in the clearance of H2O2 in erythrocytes. In the present study we investigated the role of catalase in the defence mechanism against oxidative stress using Saccharomyces cerevisiae. S. cerevisiae has two catalases, catalase A and catalase T. We constructed a double mutant (acatalasaemic mutant) unable to produce either catalase A or catalase T, and compared it with wild-type and single-mutant cells. The acatalasaemic mutant cells showed a similar growth rate to wild-type cells under non-oxidative stress conditions, and showed a similar susceptibility to H2O2 stress in the exponential growth phase. The acatalasaemic mutant cells at stationary phase were, however, much more sensitive to H2O2 stress than wild-type and single-mutant cells. Moreover, the ability of acatalasaemic and single-mutant cells to show adaptation to 2 mM H2O2 was distinctly inferior to that of wild-type cells. These results suggest that catalase is not essential for yeast cells under normal conditions, but plays an important role in the acquisition of tolerance to oxidative stress in the adaptive response of these cells.
关于过氧化氢酶在人体红细胞中对过氧化氢解毒作用的重要性，争议仍在继续。有人认为过氧化氢酶在红细胞清除过氧化氢的过程中不起作用。在本研究中，我们利用酿酒酵母研究了过氧化氢酶在抗氧化应激防御机制中的作用。酿酒酵母有两种过氧化氢酶，即过氧化氢酶A和过氧化氢酶T。我们构建了一个无法产生过氧化氢酶A或过氧化氢酶T的双突变体（无过氧化氢酶突变体），并将其与野生型和单突变体细胞进行比较。在非氧化应激条件下，无过氧化氢酶突变体细胞的生长速率与野生型细胞相似，并且在指数生长期对过氧化氢应激的敏感性也相似。然而，处于稳定期的无过氧化氢酶突变体细胞对过氧化氢应激的敏感性比野生型和单突变体细胞高得多。此外，无过氧化氢酶和单突变体细胞对2 mM过氧化氢表现出适应性的能力明显低于野生型细胞。这些结果表明，过氧化氢酶在正常条件下对酵母细胞不是必需的，但在这些细胞的适应性反应中，对获得氧化应激耐受性起着重要作用。
