Electron-spin-resonance evidence for enzymic reduction of oxygen to a free radical, the superoxide ion.
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It is concluded that the species observed is the superoxide ion, O(2) (-), and that the stability of this ion is greatly increased in alkaline solution.Abstract:
1. An electron-spin-resonance signal with g( parallel)2.08 and g( perpendicular)2.00 is observed by the rapid-freezing technique during the oxidation of substrates by molecular oxygen catalysed by xanthine oxidase at pH10. 2. The intensity of this signal is shown to depend on oxygen rather than on enzyme concentration, indicating that it is due to an oxygen free radical and not to the enzyme. 3. The same species is shown to be produced in the reaction at pH10 between hydrogen peroxide and periodate ions. Studies with this system have facilitated comparison of the properties of the oxygen radical with data in the literature on the products of pulse radiolysis of oxygenated water over a wide pH range. 4. It is concluded that the species observed is the superoxide ion, O(2) (-), and that the stability of this ion is greatly increased in alkaline solution. A mechanism explaining the alkaline stability is proposed. 5. The importance of O(2) (-) in the enzymic reaction is discussed.read more
Citations
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References
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Journal ArticleDOI
Sudden freezing as a technique for the study of rapid reactions.
TL;DR: Avis, P. G., Bergel, F., Bray, R. C. & Beinert, H. H. (1959).
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Direct studies on the electron transfer sequence in xanthine oxidase by electron paramagnetic resonance spectroscopy. ii. kinetic studies employing rapid freezing.
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Direct Studies on the Electron Transfer Sequence in Xanthine Oxidase by Electron Paramagnetic Resonance Spectroscopy I. TECHNIQUES AND DESCRIPTION OF SPECTRA
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The chemistry of xanthine oxidase. 5. Electron-spin resonance of xanthine oxidase solutions
TL;DR: It seems to the present authors that molybdenum should replace iron in this formulation before it could be accepted, and a simple explanation of the resonance phenomenon may be given.
Journal ArticleDOI
The Use of Chemiluminescent Compounds as Possible Indicators of Radical Production during Xanthine Oxidase Action
TL;DR: The present results clearly show that the light intensity in the system liver xanthine oxidase-hypoxanthineluminol is related to the reaction velocity and not to the endproduct concentration, and appears likely that the luminescence is the result of the production of Oior OH radicals during the oxidation, by oxygen, of reduced enzyme.
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