Phenoxyacetic acid induces glutathione-dependent detoxification and depletes the glutathione pool in Penicillium chrysogenum

Enzymes of the glutathione-dependent detoxification pathway (glutathione S-transferase and gamma-glutamyltranspeptidase)(1)) were induced, and the glutathione pool was completely depleted by phenoxyacetic acid in Penicillium chrysogenum mycelia incubated for 15 h in a culture medium containing lactose as a carbon source and sodium glutamate as a nitrogen source. A significant increase in both the oxidised glutathione concentrations and the glutathione reductase activities were also observed. 1-Chloro-2,4-dinitrobenzene - a potent substrate and inducer of glutathione S-transferase - initiated very similar physiological changes but no p-lactam production could be detected in this case. When (NH4)(2)HPO4 was used as a nitrogen source the penicillin biosynthesis was repressed and the induction of gamma-glutamyltranspeptidase by phenoxyacetic acid was hindered considerably.