Isozymes of superoxide dismutase from Heliobacillus mobilis

Abstract

The supernatant of cell lysates from Heliobacillus mobilis contains two superoxide dismutase (SOD) bands as revealed by activity staining of gels from non-denaturing PAGE. These SODs were partially purified by ammonium sulfate fractionation, DEAE-anion exchange, gel-permeation, and hydroxyapatite column chromatographies. Two SOD fractions were separated from each other on DEAE chromatography. The level of total SOD activity is extremely low in cells grown under strictly anaerobic photosynthetic conditions. However, when the cell culture was exposed to air, the total SOD activity of the cells very rapidly increased 4 to 8-fold in 15 - 30 min. When 1 mM paraquat was added in addition, the total activity increased 10 to 12-fold in 15 - 30 min. Increasing the paraquat concentration beyond 1 mM did not increase the SOD activities further. The both SOD activities were not inhibited by H2O2 or by KCN treatment, indicating that these SODs are Mn-SODs.