Purification, biochemical characterization and DNA protection against oxidative damage of a novel recombinant superoxide dismutase from psychrophilic bacterium Halomonas sp. ANT108.

A novel superoxide dismutase (referred hereafter to as HsSOD) from the psychrophilic bacterium Halomonas sp. ANT108 was purified and characterized. Escherichia coli (E. coli) was selected as the expression host. After recombinant HsSOD (rHsSOD) was purified, the specific activity was determined to be 213.47 U/mg with a purification ratio of approximately 3.61-fold. SDS-PAGE results demonstrated that rHsSOD has the molecular weight of 31.3 kDa, and type identification revealed that it belongs to Cu/Zn SOD. The optimum activity of rHsSOD was at 35 °C and 28% of its maximum activity remained at 0 °C. Further enzymatic assays indicated that rHsSOD exhibited thermal instability with a half-life of 20 min at 60 °C. Moreover, Cu and Zn significantly promoted rHsSOD activity. The values of K and V were 0.33 mM and 476.19 U/mg, respectively. Interestingly, rHsSOD could avoid DNA strand breakage formed by metal-catalyzed oxidation, demonstrating its antioxidant capacity. To summarize, the results suggested that rHsSOD has relatively high catalytic efficiency and oxidation resistance at low temperatures.