GLUTATHIONE METABOLISM AND PROTECTION AGAINST OXIDATIVE STRESS CAUSEDBY PEROXIDES IN PENICILLIUM-CHRYSOGENUM

The filamentous fungus Penicillium chrysogenum showed remarkable resis tance to the oxidative stress caused by high concentrations of either hydrogen peroxide (0.35-0.70 M) or tert-butyl hydroperoxide (tert-BOOH , 0.5-2.0 mM), which could be explained well with high levels of gluta thione (GSH) peroxidase and catalase activities. The majority of exoge nous H2O2 was likely removed by catalase from the cells while tert-BOO H was likely eliminated mainly by the GSH-dependent pathways. The GSH pool decreased considerably at high tert-BOOH concentrations, the glut athione disulphide (GSSG) pool increased at high H2O2 and tert-BOOH co ncentrations, meanwhile all the peroxide concentrations tested increas ed markedly the intracellular peroxide concentration. All the enzyme a ctivities taking part in the glutathione metabolism (glutathione perox idase, glutathione reductase, gamma-glutamyltranspeptidase and glutath ione producing activities) except glutathione S-transferase increased significantly after exposing mycelia to both peroxides while the speci fic glucose-6-phosphate dehydrogenase and catalase activities remained unchanged. In the presence of 0.5 mM diamide both GSSG and GSH concen trations as well as the glutathione reductase and glutathione producin g activities were elevated but no significant changes were found in th e intracellular peroxide concentration or in any of the other enzyme a ctivities examined. (C) 1997 Elsevier Science Inc.