Peroxidative activity of human Cu,Zn-superoxide dismutase.
In addition to the usual superoxide dismutation activity, Cu,Zn-superoxide dismutase (SOD) has a peroxidative function that utilizes its own dismutation product, H2O2 as a substrate. The peroxidative activity of human Cu,Zn-SOD was studied by using a chromogen, 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonate) (ABTS) which reacts with OH radicals to form ABTS+. The optimal pH for the peroxidative activity of human Cu,Zn-SOD was 7.6-9.5. The peroxidative activity retained about 50% of the maximum activity when exposed at 40 degrees C for 5 min. The peroxidative activity showed a typical Michaelis-Menten kinetics for ABTS and H2O2 whose K(m) values were 16 microM and 9.3 mM, respectively. The peroxidative activity of human Cu,Zn-SOD was inhibited about 60% by the copper chelator, diethyldithiocarbamate (DDC) at 10 microM while the dismutation activity was not inhibited under a similar condition. We found that there are differences in the effects of temperature and DDC on the dismutation and peroxidative activities of human Cu,Zn-SOD. These results suggest that the amino acid residues which affect the activities of this enzyme may be different between dismutation and peroxidation.
Kim
S M
SM
Department of Genetic Engineering, College of Natural Science and Engineering, Chongju University, Korea.
Kang
J H
JH
D052160:Benzothiazoles; D002614:Chelating Agents / Q000494:pharmacology; D002863:Chromogenic Compounds; D004050:Ditiocarb / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D010544:Peroxidases / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013451:Sulfonic Acids; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013696:Temperature
D052160:Benzothiazoles; D002614:Chelating Agents; D002863:Chromogenic Compounds; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D017665:Hydroxyl Radical; D004050:Ditiocarb; D010544:Peroxidases; D013482:Superoxide Dismutase