Purification and Properties of Superoxide Dismutase from Bacillus circulans

Abstract

Superoxide dismutase (SOD) was purified from Bacillus circulans IFO 3329 to an electrophoretically homogeneous state and partially characterized. The purification procedure involved (NH₄)₂SO₄ fractionation, column chromatography on DEAE-Sephadex A-50 and gel filtration on Sephadex G-100. The molecular weight and subunit molecular weight of the purified enzyme were estimated to be 46,000 and 26,000, respectively. The isoelectric point of the enzyme was about pH 5.2. The purified enzyme remained stable at pH 7.0 and 20°C for 36 hr, but rapidly inactivated above pH 8.0 and below pH 5.0. SOD was stable at pH 7.0 up to 40°C but was rapidly inactivated at temperatures above that. Metal ions had little effect on the SOD activity. The absorption maximum in the visible range was found at 475 nm, and the enzyme was red-purple in color and cyanide-insensitive. These results suggest that the enzyme is a Mn-containing SOD.