Superoxide Dismutase from Mycobacterium lepraemurium

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Abstract
Mycobacterium lepraemurium, strain Hawaii, grown on 1% Ogawa egg yolk medium containing hemin, was extremely rich in superoxide dismutase [EC 1.15.1.1]. This enzyme accounted for at least 7% of total proteins in the crude extracts, as determined by immunological procedures. The enzyme was purified about 18.5-fold from the crude extracts by streptomycin treatment, ammonium sulfate fractionation, and Sephadex G-100 gel filtration. The homogeneity of the purified enzyme was established by polyacrylamide gel electrophoresis, analytical ultracentrifugation, and irnmunodiffusion. The molecular weight of the enzyme was estimated to be approximately 45,000 by sedimentation equilibrium analysis, whereas that of the subunit was 22,000 as determined by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The enzyme was found to contain 1.29 g atom of manganese per mol by atomic absorption spectroscopy. In addition, a small but significant amount of iron was found. The amino acid composition was similar to that of the superoxide dismutase from Mycobacterium smegmatis. Superoxide dismutase is the first enzyme which has been isolated and characterized from M. lepraemurium.