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

Enzymes of glutathione metabolism and GSH content in copper-treated Scenede smus bijugatus cells and the synthesis of metal-binding peptides are report ed in this investigation. Progressive depletion of GSH content in the cells was observed with increasing concentrations of copper. There was an increa se in the protein thiol content while the non-protein thiol content decreas ed. There was an initial elevation and later decrease in the hydrogen perox ide level in the cells. Copper stress increased the activities of gamma -gl utamylcysteine synthetase, GSH S-transferase and GSH-peroxidase and decreas ed 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 phytoche latins. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.