Superoxide dismutase (SOD) is an antioxidant enzyme which protects cells from destructive effects of superoxide anion. This enzyme catalyze dismutation of anion superoxide into oxygen and hydrogen peroxide. This unique enzyme is used in the treatment of diseases caused by oxidative stress. It is also used as an anti-inflammatory enzyme in medical science. So far, many efforts have been made to improve the efficiency and stability of this enzyme because of its importance in medical application. The purpose of this research is cloning, expression, purification and characterization of a novel CuZn-SOD from Avicennia marina (AmCuZn-SOD).To this aim, the coding sequence of CuZn-SOD was cloned into expression vector pET-28a. Then this recombinant plasmid was transformed to Escherichia coli strain Rosetta (DE3). The protein was expressed as a His-tag fusion protein after induction with IPTG in four different conditio in the medium with no metals, in the presence of Cu 2+ , Zn 2+ and both Cu 2+ and Zn 2+ . The SOD in these three conditions was produced and purified by affinity chromatography. The expressed protein contains 188 amino acid residues and its molecular weight is 19 kDa. The activity of this enzyme was determined presence of Cu 2+ and/or Zn 2+ as well as control medium. The stability of the enzyme was measured in the temperature range of 25- 75°C and pH range of 3-12. Base on the results we found that AmSOD has its best activity by addition of both copper and zinc ion to culture of bacteria, The optimum temperature was 25°C and the optimum pH was pH3-8. These results open new window for application of recombinant form of AmSOD in the medicine and industry. Key words: Antioxidant Enzyme; Superoxide Dismutase; Avicennia Marina; Heterologous expression; Activity; Stability
