An iron-containing superoxide dismutase from the strict anaerobe Desulfovibrio desulfuricans (Norway 4).

Superoxide dismutase, the enzyme which catalyzes the dismutation of superoxide free radicals (formula: see text) has been purified to homogeneity from the strict anaerobe sulfate-reducing bacterium Desulfovibrio desulfuricans (Norway 4). Its molecular weight is 43,000 and it is composed of two subunits of equal size which are not covalently bound. The enzyme was found to contain iron by atomic absorption and the absence of acid-labile sulfur indicates that it is not an iron-sulfur protein. Electron paramagnetic resonance spectrum revealed that iron occurs in a high spin ferric form. The ultraviolet and visible absorption spectra of the enzyme are presented, as are the results of amino-acid analysis. The data reported allow to conclude that this superoxide dismutase isolated from a strict anaerobe exhibits similar physico-chemical properties as compared to the iron-containing dismutases found in aerobic microorganisms. The significance of the presence of a superoxide dismutase in this strict anaerobe sulfate reducer is discussed.