Purification and properties of mangano-superoxide dismutase from a strain of alkaliphilic Bacillus

A mangano-superoxide dismutase (EC 1.15.1.1) was purified to homogeneity from a strain of alkaliphilic Bacillus for the first time. The purified protein, with an isoelectric point of pH 4.5, had a molecular mass of approximately 50 kDa and consisted of two identical subunits (25 kDa). The N-terminal amino acid sequence was Ala-Tyr-Lys-Leu-Pro-Glu-Leu-Pro-Tyr-Ala-Ala-Asn-Ala-Leu-Glu-Pro-His-Ile- Asp-Glu-Ala. The optimum pH and temperature for the reaction were 7.5 and 35 degrees C, respectively. The properties of the superoxide dismutase were compared with those of the enzyme from thermophilic Bacillus stearothermophilus.