IDENTIFICATION OF IRON SUPEROXIDE-DISMUTASE AND A COPPER ZINC SUPEROXIDE-DISMUTASE ENZYME-ACTIVITY WITHIN THE MARINE CYANOBACTERIUM SYNECHOCOCCUS SP WH-7803/

Three constitutive forms of superoxide dismutase activity have been de monstrated in the cyanobacterial marine picoplankter Synechococcus sp. WH 7803 using polyacrylamide gel activity staining techniques. A prot ein which gave a positive non-haem iron stain on native polyacrylamide gels exhibited N-terminal similarity to both the iron superoxide dism utase and the manganese superoxide dismutase of Escherichia coli. The metal prosthetic group of each of the three activity bands was charact erised by analysing their differential sensitivities to 5 mM H2O2, 2 m M cyanide and 2 mM of the copper chelator diethyldithiocarbamate. Thre e distinct superoxide dismutase activities were observed, an iron supe roxide dismutase, a copper/zinc superoxide dismutase and a third form which has not been identified. Growth of Synechococcus cells in ASW me dium containing no added iron resulted in no alteration in the activit y of the iron superoxide dismutase. Growth of cultures in the absence of copper or zinc resulted in differential changes in the activities o f the copper/zinc superoxide dismutase and the unidentified superoxide dismutase.