A MANGANESE AND IRON-CONTAINING SUPEROXIDE DISMUTASE FROM RHODOCOCCUS BRONCHIALIS

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A superoxide dismutase (EC 1.15.1.1) was purified 113-fold with a yield of 38% from the crude extract of Rhodococcus bronchialis (Gordona bronchialis). The purified enzyme was homogeneous as judged by polyacrylamide gel electrophoresis, analytical ultracentrifugation and immunological procedures. The molecular weights of the enzyme and its subunit were estimated to be approximately 80, 000 and 21, 000, by sedimentation equilibrium analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively. The amino acid composition was similar to that of the enzyme from Mycobacterium smegmatis. Metal analysis showed that the enzyme contained approximately 2.2 and 0.9 atoms of manganese and iron per mol, respectively. Correlation of enzymic activity, and manganese and iron contents in fractions of gel filtration on a Sephadex G-100 column indicated that both the metals were tightly bound to the enzyme.