Purification and characterization of superoxide dismutase from the rhizomes of zingiberaceae plants

Abstract

Superoxide dismutase (SOD, EC 1.15.1.1) was metalloenzyme or antioxidant enzyme. It catalyzes the disproportionation of harmful superoxide anionic radical to hydrogen peroxide and molecular oxygen. Due to its antioxidative effects, SOD has long been applied in medicinal treatment, cosmetic and other chemical industries. In this study, aqueous extracts and crude proteins from the rhizomes of fifteen Zingiberaceae plants were tested were tested for SOD activity. The Curcuma aeruginosa showed a highest SOD activity. SOD from the rhizomes of C. aeruginosa was purified by ammonium sulphate precipitation, DEAE cellulose and Superdex 75 column chromatography. A 4.36 fold purification and on overall yield of 2.51% were achieved. The purified enzyme was 31.5 kDa as judged by SDS-PAGE. The enzyme has a pH optimum of 4.0. It was stable over a wide range of temperatures -20 – 45 ºC. It belongs to the MnSOD category due to the fact that it was insensitive to KCN or hydrogen peroxide inhibitor. The Mn2+and Fe2+ ions stimulated SOD inhibition activity when increased metal ions concentrations. Maximum activity was observed to 333.7 and 254.1 µmol/min/mg for NBT, and riboflavin respectively. The Km of enzyme was found to be 57.31, and 1.51 M for NBT, and riboflavin respectively. This is the first report for SOD from C. aeruginosa, a traditionally used Thai medicinal plants.