Purification and characterization of a superoxide dismutase from Panax ginseng

A superoxide dismutase (SOD) with the molecular weight of 31,079 has been purified as a homodimer from Panax ginseng by employing neutral pH buffer extraction, ammonium sulfate precipitation, isoelectric point precipitation and ion exchange methods. The enzyme's specific activity determined by an improved Marklund method was 9480.43 U/mg. Metal analysis showed that the SOD contained iron with the stoichiometry of 0.9 ± 0.3 Fe/subunit and exhibited high thermal stability (70 °C) over the pH range from 4.0 to 9.0. Its maximum absorption wavelength was 278 nm and it was sensitive to hydrogen peroxide, trichloromethane-ethanol and urea. These results indicate that the enzyme is an iron SOD.