Involvement of the Superoxide Anion Radical in the Autoxidation of Pyrogallol and a Convenient Assay for Superoxide Dismutase
TL;DR: The autoxidation of pyrogallol was investigated in the presence of EDTA in the pH range 7.9–10.6, indicating an almost total dependence on the participation of the superoxide anion radical, O2·−, in the reaction.
Abstract: The autoxidation of pyrogallol was investigated in the presence of EDTA in the pH range 7.9–10.6.
The rate of autoxidation increases with increasing pH. At pH 7.9 the reaction is inhibited to 99% by superoxide dismutase, indicating an almost total dependence on the participation of the superoxide anion radical, O2·−, in the reaction. Up to pH 9.1 the reaction is still inhibited to over 90% by superoxide dismutase, but at higher alkalinity, O2·− -independent mechanisms rapidly become dominant.
Catalase has no effect on the autoxidation but decreases the oxygen consumption by half, showing that H2O2 is the stable product of oxygen and that H2O2 is not involved in the autoxidation mechanism.
A simple and rapid method for the assay of superoxide dismutase is described, based on the ability of the enzyme to inhibit the autoxidation of pyrogallol.
A plausible explanation is given for the non-competitive part of the inhibition of catechol O-methyltransferase brought about by pyrogallol.
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TL;DR: O2- oxidizes the [4Fe-4S] clusters of dehydratases, such as aconitase, causing-inactivation and release of Fe(II), which may then reduce H2O2 to OH- +OH..
Abstract: O2- oxidizes the [4Fe-4S] clusters of dehydratases, such as aconitase, causing-inactivation and release of Fe(II), which may then reduce H2O2 to OH- +OH.. SODs inhibit such HO. production by scavengingO2-, but Cu, ZnSODs, by virtue of a nonspecific peroxidase activity, may peroxidize spin trapping agents and thus give the appearance of catalyzing OH. production from H2O2. There is a glycosylated, tetrameric Cu, ZnSOD in the extracellular space that binds to acidic glycosamino-glycans. It minimizes the reaction of O2- with NO. E. coli, and other gram negative microorganisms, contain a periplasmic Cu, ZnSOD that may serve to protect against extracellular O2-. Mn(III) complexes of multidentate macrocyclic nitrogenous ligands catalyze the dismutation of O2- and are being explored as potential pharmaceutical agents. SOD-null mutants have been prepared to reveal the biological effects of O2-. SodA, sodB E. coli exhibit dioxygen-dependent auxotrophies and enhanced mutagenesis, reflecting O2(-)-sensitive biosynthetic pathways and DNA damage. Yeast, lacking either Cu, ZnSOD or MnSOD, are oxygen intolerant, and the double mutant was hypermutable and defective in sporulation and exhibited requirements for methionine and lysine. A Cu, ZnSOD-null Drosophila exhibited a shortened lifespan.
3,298 citations
TL;DR: Hydrogen peroxide stimulated the autoxidation and superoxide dismutase inhibited the hydrogen peroxide-induced oxidation, results which suggest the participation of hydrogenperoxide in autoxidated and in the generation of superoxide radical.
1,480 citations
1,475 citations
TL;DR: It is concluded that EDRF from artery and vein is either NO or a chemically related radical species, which possesses identical properties in their interactions with oxyhemoproteins.
Abstract: The objective of this study was to elucidate the close similarity in properties between endothelium-derived relaxing factor (EDRF) and nitric oxide radical (NO). Whenever possible, a comparison was also made between arterial and venous EDRF. In vascular relaxation experiments, acetylcholine and bradykinin were used as endothelium-dependent relaxants of isolated rings of bovine intrapulmonary artery and vein, respectively, and NO was used to relax endothelium-denuded rings. Oxyhemoglobin produced virtually identical concentration-dependent inhibitory effects on both endothelium-dependent and NO-elicited relaxation. Oxyhemoglobin and oxymyoglobin lowered cyclic guanosine monophosphate (cGMP) levels, increased tone in unrubbed artery and vein, and abolished the marked accumulation of vascular cGMP caused both by endothelium-dependent relaxants and by NO. The marked inhibitory effects of oxyhemoglobin on arterial and venous relaxant responses and cGMP accumulation as well as its contractile effects were abolished or reversed by carbon monoxide. These observations indicate that EDRF and NO possess identical properties in their interactions with oxyhemoproteins. Both EDRF from artery and vein and NO activated purified soluble guanylate cyclase by heme-dependent mechanisms, thereby revealing an additional similarity in heme interactions. Spectrophotometric analysis disclosed that the characteristic shift in the Soret peak for hemoglobin produced by NO was also produced by an endothelium-derived factor released from washed aortic endothelial cells by acetylcholine or A23187. Pyrogallol, via the action of superoxide anion, markedly inhibited the spectral shifts, relaxant effects, and cGMP accumulating actions produced by both EDRF and NO. Superoxide dismutase enhanced the relaxant and cGMP accumulating effects of both EDRF and NO. Thus, EDRF and NO are inactivated by superoxide in a closely similar manner. We conclude, therefore, that EDRF from artery and vein is either NO or a chemically related radical species.
1,185 citations
TL;DR: Article de synthese traitant de la pharmacologie de l'oxyde nitrique, du facteur EDRF and du GMP cyclique dans les vaisseaux sanguins and les thrombocytes, de la formation, de the liberation and du metabolisme de l’endothelium derived NO (EDNO).
Abstract: Article de synthese traitant de la pharmacologie de l'oxyde nitrique, du facteur EDRF et du GMP cyclique dans les vaisseaux sanguins et les thrombocytes, de l'isolation et de l'identification du facteur EDRF comme de l'oxyde nitrique, et de la formation, de la liberation et du metabolisme de l'endothelium derived NO (EDNO)
1,005 citations
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TL;DR: The demonstration that O2·- can reduce ferricytochrome c and tetranitromethane, and that superoxide dismutase, by competing for the superoxide radicals, can markedly inhibit these reactions, is demonstrated.
12,468 citations
TL;DR: It is proposed that the autoxidation of epinephrine proceeds by at least two distinct pathways, only one of which is a free radical chain reaction involving O2- and hence inhibitable by superoxide dismutase.
7,872 citations
TL;DR: Wansbrough-Jones as discussed by the authors gave the manuscript of this paper to Professor Sir William Pope, but the final revision for the press had not been made and in its original from the paper was not suitable for publication in an English journal; but since, Professor Haber had considered carefully how he wished to present the results embodied in it, the form and sequence of the paper remain unmodified.
Abstract: [ Note by Dr. O. H. Wansbrough-Jones —Shortly before Professor Haber died, he gave the manuscript of this paper to Professor Sir William Pope. The final revision for the press had not been made and in its original from the paper was not suitable for publication in an English journal. Considerable alterations in the wording have accordingly been made; but since, Professor Haber had considered carefully how he wished to present the results embodied in it, the form and sequence of the paper remain unmodified. The paper is, further, a sequel to some communications in German periodicals which may not be familiar to its readers. In an attempt to make it more quickly understandable, while keeping it as far as possible as it was left by Professor Haber, the following summary has been added.
2,318 citations
TL;DR: The properties of an enzyme that transfers the methyl group of S-adenosylmethionine to the hydroxyl group in position 3 of epinephrine and other catechols are described.
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TL;DR: Chicken liver was not unique in possessing distinct superoxide dismutases in cytosol and in mitochondrial compartments, but it lends support to the theory that mitochondria have evolved from aerobic prokaryotes, which entered into an endocellular symbiosis with a protoeukaryote.
861 citations