Co-ordination of the nitrate and nitrite assimilation, the glutathione andfree radical metabolisms, and the pentose phosphate pathway in Penicilliumchrysogenum

The specific glutathione reductase (GR) and glucose-6-phosphate dehydrogena se (GGPD) activities increased significantly in Penicillium chrysogenum gro wn on glucose in the presence of either nitrate or nitrite. These changes k ept the intracellular peroxide levels low and prevented the onset of any gl utathione/glutathione disulphide redox imbalances. On the other hand, the s pecific activity of several other glutathione metabolic enzymes including g lutathione peroxidase, glutathione S-transferase, gamma-glutamyltranspeptid ase and the glutathione producing activity was not effected by NO3- and NO2 -. When P. chrysogenum mycelia were challenged with oxidative stress caused by high concentrations of H2O2, tert-butyl hydroperoxide, menadione, diami de or phenoxyacetic acid the intracellular peroxide concentrations increase d significantly, and the nitrate reductase and nitrite reductase activities were eliminated. When glucose was replaced with lactose the GR and GGPD ac tivities were not influenced by the nitrogen sources but in this case the i ntracellular GSH concentration was twice higher than that observed with glu cose.