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Nitroxide-stimulated H2O2 decomposition by peroxidases and pseudoperoxidases
Free Radical Research Communications
|January 1, 1992
Summary
Nitroxide free radicals exhibit antioxidant activity by catalyzing hydrogen peroxide (H2O2) breakdown into oxygen. This distinct mechanism, separate from superoxide dismutation, may protect against cardiac reperfusion injury.
Area of Science:
- Biochemistry
- Free Radical Chemistry
- Antioxidant Mechanisms
Background:
- Nitroxide free radicals interact with heme proteins like hemoglobin and myoglobin.
- These interactions can influence reactive oxygen species metabolism.
Purpose of the Study:
- To investigate the catalatic activity of nitroxides in decomposing hydrogen peroxide (H2O2).
- To elucidate the antioxidant mechanisms of nitroxides beyond superoxide dismutation.
Main Methods:
- Studied the interaction of nitroxides with heme proteins and phenols.
- Investigated H2O2 decomposition in the presence of nitroxides.
- Assessed the effect of glutathione and sodium borohydride on the reaction.
- Monitored free radical formation using spin-trapping techniques.
Main Results:
- Nitroxides induce a catalase-like conversion of H2O2 to O2 without significant consumption.
- A proposed mechanism involves one-electron oxidation to an immonium oxene.
- Nitroxides suppress free radical formation by heme proteins, inhibiting glutathionyl radical spin-trapping.
- This activity is distinct from superoxide dismutating effects and is inhibited by glutathione.
Conclusions:
- Nitroxides possess a unique antioxidant activity involving H2O2 decomposition.
- This catalatic activity may contribute to their protective effects in conditions like cardiac reperfusion injury.