Purification and Properties of Ironcontaining Superoxide Dismutase from Spirulina maxima

The isozyme of SOD in Spirulina maxima with four bands by gradient electrophoresis was identified as Fe--SOD, which was purified by ammonium sulfate fractionation followed by DEAECelluose and Sephadex G-100 column chromatography. The molecular weight of the enzyme is 39. 3KD, and that of its subunit molecular mass is 20KD. Metal analysis showed that the Fe-SOD contains about 0. 55 atom of iron per subunit. The enzyme exhibits one absorption maximum at 275. 8nm. The enzyme activity could be inhibited by H_2O_2 but unaffected by KCN. The Fe-enzyme contains more alanine residues. The ratio of acid amino acid and alkaline amino acid is similar to lower plants and procaryotes, obviously higher than those of higher plants.