PURIFICATION OF COPPER-ZINC SUPEROXIDE DISMUTASE FROM HUMAN ERYTHROCYTES AND PARTIAL CHARACTERIZATION

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-celltilose 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 degrees C. Activation energy was calculated as 16.856 kj/mol and initiation of denaturation temperature was calculated as 19 degrees C. Turnover number (k(cat)) and catalytic efficiency (k(cat)/Km) were found to be 1667 s(-1) and 5.6x10(5) s(-1). mM(-1) Xanthine(-1), respectively. The enzyme was found to have good storage stability as 93.6% of initial activity after 28 days of storage in 50% glycerol solution at -20 degrees C.