Effect of cadmium on antioxidative enzymes, glutathione content, and glutathionylation in tall fescue

The aim of this work was to assess the effect of different Cd2+ concentrations on some antioxidant enzymes in Festuca arundinacea. Increased activities of ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione S-transferase, and glutathione reductase were ascertained in response to low Cd-2+ concentrations (0 - 20 mu M), whereas the enzyme activities were less increased or decreased at a higher Cd2+ dosage (50 mu M) and a longer exposure. The content of reduced glutathione (GSH) decreased significantly with increasing Cd2+ concentrations, whereas the content of oxidized glutathione (GSSG) increased proportionally to the amount of Cd2+ applied. Further experiments, performed by incubating the enzyme extracts with oxidized glutathione, evidenced that the addition of GSSG to the incubation mixtures caused significant decreases of some enzymatic activities. Finally, the effect of glutathione S-transferase, FaGST I, extracted from fescue seedlings and purified till homogeneity, on these enzyme activities was investigated. It was found that FaGST I enhanced the decreased enzymatic activities caused by GSSG.