THE INFLUENCE OF METALS ON THE ANTIOXIDANT ENZYME,

Cyanobacteria have a highly evolved antioxidant system that catalyzes the harmful oxy radicals produced during photosynthesis. The differential response of superoxide dismutase (SOD), nitrogenase, growth and physiological processes in the presence of four different metals ions at varying concentrations were investigated in the heterocystous cyanobacterium, Anabaena variabilis Kütz. Growth and enzyme activities were influenced by the metal ions. SOD activity was optimum at 100 mcM concentration of FeSO4 but nitrogenase activity decreased in the presence of the metal ions. SOD activities increased with increasing concentrations of MnSO4 while nitrogenase activities decreased when compared with control. In the presence of CuSO4, all the enzyme activities were increased compared with control and optimal enzyme activity was observed at 300 mcM concentration. In the presence of ZnSO4, nitrogenase and glutamine synthetase activities reduced with increasing concentrations of the metal salt while SOD activity increased in direct proportion with metal concentration. The differential expression of FeSOD and MnSOD in the cells of A. variabilis were also investigated by electrophoresis and are presented in this paper