Identification and kinetic characterization of a novel superoxide dismutase from Avicennia marina: An antioxidant enzyme with unique features.

A novel Cu/Zn-superoxide dismutase was extracted from Avicennia marina and purified. The sample was collected from Khamir port located in the north shore of Persian Gulf. The purification procedure comprised of (NH4)2SO4 precipitation followed by CM-Sephadex C-50 and DEAE-Sepharose chromatography, and gel filtration chromatography (Sephadex G-75). The enzyme with a characteristic molecular weight of 31kDa, measured by SDS-page, showed its highest catalytic efficiency at pH 8.0 and 50°C. Its activity was greatly inhibited by cyanide and hydrogen peroxide. The pH profile showed that the enzyme could maintain most of its activity at pH values ranging from 5 to 10. The temperature profile of this enzyme showed a broad range of activity compared with other superoxide dismutases. Catalytic hydrolysis rate followed Michaelis-Menten equation. The values of kcat and Km were obtained from Michaelis-Menten plot as 107000s-1 and 11.5μmol respectively. The evidences from kinetic and thermodynamic parameters suggest that Avicennia marina superoxide dismutase (AmSOD) can be used as a suitable enzyme for biotechnological and pharmacological applications.