Purification of copper-zinc superoxide dismutase from human erythrocytes and partial characterization

Abstract

Copper-zinc superoxide dismutase (CuZnSOD; E.C:1.15.1.1) catalyzes the dismutation of the superoxide radical to hydrogen peroxide and oxygen. In this study, CuZnSOD was isolated from human erythrocytes using DEAE-cellulose chromatography and copper chelate affinity chromatography. The enzyme was purified 196.3 fold with 33.8% efficiency. The molecular weight of CuZnSOD was determined as 20 kDa by SDS-PAGE. Vmax and Km values were determined as 5000 U/mg protein and 3.10-3 mM Xanthine, respectively. Maximum CuZnSOD activity was observed at 15°C. Activation energy was calculated as 16.856 kj/mol and initiation of denaturation temperature was calculated as 19°C. Turnover number (kcar) and catalytic efficiency (kcar/Km) were found to be 1667 s' and 5.6 x10 s s-1.mM-1 Xanthine', respectively. The enzyme was found to have good storage stability as 93.6% of initial activity after 28 days ofstorage in 50% glycerol solution at-20°C.