Responses of glutathione cycle enzymes and glutathione metabolism to copper stress in Scenedesmus bijugatus.

Enzymes of glutathione metabolism and GSH content in copper-treated Scenedesmus bijugatus cells and the synthesis of metal-binding peptides are reported in this investigation. Progressive depletion of GSH content in the cells was observed with increasing concentrations of copper. There was an increase in the protein thiol content while the non-protein thiol content decreased. There was an initial elevation and later decrease in the hydrogen peroxide level in the cells. Copper stress increased the activities of gamma-glutamylcysteine synthetase, GSH S-transferase and GSH-peroxidase and decreased the activity of GSSG-reductase. These results suggest that copper alters the equilibrium between synthesis and utilization of GSH either due to its antioxidant role or by serving as a precursor in the synthesis of phytochelatins.