The peroxidase activity of superoxide dismutase (SOD) has been attributed to the increased lipid peroxidation observed during the reaction between linoleic acid, SOD and H2O2. The copper-bound hydroxyl radical was proposed to abstract an hydrogen atom from linoleate and initiate lipid peroxidation. To better understand the mechanism of SOD/H2O2-catalyzed lipid peroxidation, we have used S-nitrosoglutathione (GSNO) as an antioxidant probe. Addition of H2O2 (1 mM) to an incubation mixture containing egg phosphatidylcholine liposomes (250 μg/ml) and SOD (200 μg/ml) caused an increase in the formation of conjugate diene which was inhibited by the addition of diethylenetriaminepentaacetic acid (DTPA). Addition of GSNO caused a dose-dependent increase in time-lag for conjugate diene formation. Nitric oxide released from GSNO in the presence of SOD and H2O2 was measured by electron spin resonance spectroscopy. We attribute the increase in lipid peroxidation caused by SOD and H2O2 to the copper ions released from SOD that subsequently catalyzes the lipid hydroperoxide-dependent oxidation. The antioxidant activity of GSNO is attributed to the copper ion dependent release of nitric oxide, which acts as a chain breaking antioxidant. We conclude that GSNO can act as a potent antioxidant in biological systems where free copper ions released from metalloproteins catalyze peroxidation of lipid.
|Original language||English (US)|
|State||Published - Mar 20 1998|
ASJC Scopus subject areas
- Molecular Biology