IMPORTANCE OF CATALASE IN THE ADAPTIVE RESPONSE TO HYDROGEN-PEROXIDE - ANALYSIS OF ACATALASAEMIC SACCHAROMYCES-CEREVISIAE

Controversy about the importance of catalase in the detoxification of H2O2 in human erythrocytes continues. It has been suggested that catal ase has no role in the clearance of H2O2 in erythrocytes. In the prese nt study we investigated the role of catalase in the defence mechanism against oxidative stress using Saccharomyces cerevisiae. S. cerevisia e has two catalases, catalase A and catalase T. We constructed a doubl e mutant (acatalasaemic mutant) unable to produce either catalase A or catalase T, and compared it with wild-type and single-mutant cells. T he acatalasaemic mutant cells showed a similar growth rate to wild-typ e cells under non-oxidative stress conditions, and showed a similar su sceptibility to H2O2 stress in the exponential growth phase. The acata lasaemic mutant cells at stationary phase were, however, much more sen sitive to H2O2 stress than wild-type and single-mutant cells. Moreover , the ability of acatalasaemic and single-mutant cells to show adaptat ion to 2 mM H2O2 was distinctly inferior to that of wild-type cells. T hese results suggest that catalase is not essential for yeast cells un der normal conditions, but plays an important role in the acquisition of tolerance to oxidative stress in the adaptive response of these cel ls.