Unique Isozymes of Superoxide Dismutase inStreptomyces griseus

Two unique isozymes of superoxide dismutase (EC 1.15.1.1) were purified to apparent homogeneity fromStreptomyces griseusby a purification procedure consisting of ammonium sulfate precipitation and chromatographies on DEAE Sephacel, Sephacryl S-200, and DEAE 5PW. Superoxide dismutase I was composed of four identical subunits of 13.0 kDa. The absorption spectrum of superoxide dismutase I exhibited absorption bands at 276 and 378 nm and a broad shoulder at 530 nm. Thegvalues of electron paramagnetic resonance spectrum of superoxide dismutase I wereg1= 2.304,g2= 2.248, andg3= 2.012 and the resonance centered atg3= 2.012 was split into triplet, indicating nickel-containing superoxide dismutase. Superoxide dismutase I contained 0.89 g-atom of nickel per mole of 13.0-kDa subunit. Superoxide dismutase II was composed of four identical subunits of 22.0 kDa. The absorption spectrum of superoxide dismutase II showed the featureless absorption band in the range of 300–500 nm. Thegvalues of electron paramagnetic resonance spectrum of superoxide dismutase II weregz= 4.762,gx= 4.072, andgy= 3.742, indicating iron-containing superoxide dismutase. Superoxide dismutase II uniquely contains 0.40 g-atom of iron per mole of monomer as well as 0.43 g-atom of zinc per mole of monomer. The immunological cross-reactivity between two isozymes was not found. Nickel-containing superoxide dismutase was widely distributed within the genusStreptomyces;however, iron- and zinc-containing superoxide dismutase was not found inS. albusandS. longisporoflavus,on the basis of the immunological cross-reactivity.