Hydroxyl Radical-Generating Function of Horseradish Cu,Zn-Superoxide Dismutase

  • Eum, Won-Sik (Department of Genetic Engineering, Chongju University) ;
  • Kwon, Oh-Bin (Department of Genetic Engineering, Chongju University) ;
  • Kang, Jung Hoon (Department of Genetic Engineering, Chongju University)
  • Received : 1998.05.26
  • Accepted : 1998.06.30
  • Published : 1998.09.30

Abstract

Cu,Zn-superoxide dismutase (SOD) was purified from horseradish by using Mono Q and Superose 12 FPLC column chromatography. The native molecular mass of the purified enzyme was approximately 33 kDa, as determined by gel filtration. The subunit molecular weight, as estimated by SDS-PAGE, was 16 kDa. These results indicated that the native enzyme is a homodimer. We investigated the free radical-generating function of horseradish Cu,Zn-SOD by using a chromogen, 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) which reacts with ${\cdot}OH$ radicals to form $ABTS^{+{\cdot}}$ The formation of $ABTS^{+{\cdot}}$ was required for both active Cu, Zn-SOD and $H_2O_2$. The optimal pH for the free radical-generating activity of this enzyme was 6.0-8.0, and it retained about $40^{\circ}C$ of its maximum activity when exposed at $40^{\circ}C$ for 15 min. A neutral scavenger, ethanol, inhibited the $ABTS^{+{\cdot}}$ formation by horseradish Cu, Zn-SOD more effectively than that by the mammalian enzyme. These results suggest that the active channel of horseradish enzyme is slightly larger than that of the mammalian enzyme.

Keywords

Copper,Zinc-superoxide dismutase;Horseradish;Hydrogen peroxide;Hydroxyl radicals