Physiological and biochemical effects of cadmium toxicity in enzymes involved in nitrogen and amino—acid metabolism in tomato plants

Abstract

The activities of several enzymes related to amino—acid metabolism were investigated in tomato plants (Lycopersicon esculentum Mill. 63/5F1) in control and treated leaves and roots. Glutamine synthetase and glutamate synthase ferredoxine dependent activities rapidly declined in stress condition. In presence of cadmium, the decline of glutamine synthetase activity was retarded, while the activity of glutamate synthase significantly and more rapid declined. The activity of NADH—dependent glutamate dehydrogenase was markedly increased in presence of cadmium. Western blots analysis from cadmium treated plants, showed a decrease in chloroplastic GS (GS2) protein and an increase in cytosolic GS (GS1) and glutamate dehydrogenase (GDH) proteins. The activities of phosphoenol pyruvate carboxylase and NADP—dependent isocitrate dehydrogenase also increased in both organs of plantes treated. The activity of NAD and NADP—dependent malate dehydrogenase were decreased especially in leaves.