scholarly journals The rate of reaction of superoxide radical ion with oxyhaemoglobin and methaemoglobin

1976 ◽  
Vol 155 (3) ◽  
pp. 503-510 ◽  
Author(s):  
H C Sutton ◽  
P B Roberts ◽  
C C Winterbourn
Keyword(s):  
Superoxide Dismutase ◽  
Xanthine Oxidase ◽  
Rate Constants ◽  
Superoxide Radical ◽  
Radical Ions ◽  
Catalysed Oxidation ◽  
Rate Of Reaction ◽  
Radiolytic Reduction

Superoxide radical ions (O2-) produced by the radiolytic reduction of oxygenated formate solutions and by the xanthine oxidase-catalysed oxidation of xanthine were shown to oxidize the haem groups in oxyhaemoglobin and reduce those in methaemoglobin as in reactions (1) and (2): (see articles) Reaction (1) is suppressed by reaction (8) when [O2-]exceeds 10 muM, but consumes all the O2- generated in oxyhaemoglobin solutions when [oxyhaemoglobin] greater than 160 muM and [O2-]less than 1 nM at pH 7. The yield of reaction (2) is also maximal in methaemoglobin solutions under similar conditions, but less than one haem group is reduced per O2- radical. From studies of (a) the yield of reactions (1) and (2) at variable [haemoglobin] and rates of production of O2-, (b) their suppression by superoxide dismutase, and (c) equilibria observed with mixtures of oxyhaemoglobin and methaemoglobin, it is shown that k1/k2=0.7 +/- 0.2 and k1 = (4 +/- 1) × 10(3) M-1-S-1 At pH7, and k1 and k2 decrease with increasing pH. Concentrations and rate constants are expressed in terms of haem-group concentrations. Concentrations of superoxide dismutase observed in normal erythrocytes are sufficient to suppress reactions (1) and (2), and hence prevent the formation of excessive methaemoglobin.

Influence of milk proteins on lipid oxidation in aqueous emulsion: II. Lactoperoxidase, lactoferrin, superoxide dismutase and xanthine oxidase

1982 ◽  
Vol 49 (2) ◽  
pp. 249-263 ◽  
Author(s):  
John C. Allen ◽  
Wendy L. Wrieden
Keyword(s):  
Heat Treatment ◽  
Superoxide Dismutase ◽  
Lipid Oxidation ◽  
Xanthine Oxidase ◽  
Milk Proteins ◽  
Enzymic Activity ◽  
Aqueous Emulsion ◽  
Catalysed Oxidation ◽  
Milk And Dairy Products ◽  
Oxidative Effect

SUMMARYThe milk-related model system described by Allen & Wrieden (1982) was used to assess the effects of a number of purified milk metalloproteins, at concentrations relevant to those in milk and dairy products, on triglyceride oxidation in emulsions. Oxidations were monitored by the rate of O2 utilization (ROU) and by the thiobarbituricacid (TBA) assay. The proteins lactoferrin, lactoperoxidase, superoxide dismutase and xanthine oxidase were used either on their own or in conjunction with 10 μM-Cu2+ or Fe2+. Lactoferrin alone had little effect on oxidation, although both the iron-free and iron-saturated protein were able to protect the lipid to some extent from Fe2+-catalysed oxidation. Cu2+-catalysed oxidation was slightly promoted. Lactoperoxidase was pro-oxidative in the absence and presence of added Cu2+ or Fe2+. Heat treatment at 72°C/20 s had little effect, but oxidation was greatly reduced by treatment at 80°C/20 s. Superoxide dismutase strongly reduced the rate of lipid oxidation in the absence of added metals, but had no effect in the presence of 10 μM-Cu2+. xanthine oxidase had little effect on lipid oxidation in the absence of added metals, but was strongly pro-oxidative in the presence of 10 μ-Cu2+. Similar effects were observed down to 1 μM-Cu2+. The enzymic activity of xanthine oxidase was rapidly eliminated by 10 μM-Cu2+, but not by 10 μM-Fe2+. A moderate pro-oxidative effect was observed in the presence of 10 μM-Fe2+. Heat treatment of xanthine oxidase at 80°C/20 s reduced its lipid pro-oxidative effect in the presence of Cu2+ more effectively than treatment at 72°C/20 s.

Effects of ischemia and oxygen radicals on mucosal albumin clearance in intestine

1982 ◽  
Vol 242 (5) ◽  
pp. G448-G454 ◽  
Author(s):  
B. Grogaard ◽  
D. A. Parks ◽  
D. N. Granger ◽  
J. M. McCord ◽  
J. O. Forsberg
Keyword(s):  
Superoxide Dismutase ◽  
Xanthine Oxidase ◽  
Superoxide Radical ◽  
Arterial Occlusion ◽  
Oxidase Inhibitor ◽  
Radical Scavenger ◽  
Perfusion Rate ◽  
Xanthine Oxidase Inhibitor ◽  
Luminal Perfusion ◽  
Albumin Clearance

Mucosal albumin clearance was measured in jejunal segments of dogs under control conditions, after arterial occlusions of varying duration (15 min-4 h), and during intraluminal perfusion with hypoxanthine-xanthine oxidase. Albumin clearance rates were estimated from the luminal perfusion rate and the activity of protein-bound 125I in the perfusate and plasma. Arterial occlusion of 30-min to 4-h duration produced a significant increase in mucosal albumin clearance. The magnitude of the rise in albumin clearance was directly related to the duration of arterial occlusion. Pretreatment with superoxide dismutase, a superoxide radical scavenger, or allopurinol, a xanthine oxidase inhibitor, did not prevent the increased albumin clearance induced by 1 h of occlusion. Intraluminal perfusion with hypoxanthine-xanthine oxidase significantly increased mucosal albumin clearances. This increase was prevented by superoxide dismutase. The results of this study indicate that arterial occlusions and enzymatically generated superoxide radicals increase mucosal albumin clearance.

scholarly journals Free-radical chain oxidation of 2-nitropropane initiated and propagated by superoxide

1986 ◽  
Vol 237 (2) ◽  
pp. 505-510 ◽  
Author(s):  
C F Kuo ◽  
I Fridovich
Keyword(s):  
Superoxide Dismutase ◽  
Free Radical ◽  
Crown Ether ◽  
Co Oxidation ◽  
Xanthine Oxidase ◽  
Superoxide Radical ◽  
Radical Chain ◽  
Chain Oxidation ◽  
Radical Chain Oxidation ◽  
Oxidase Reaction

The superoxide radical O2.-, whether produced by the xanthine/xanthine oxidase reaction or infused as KO2, solubilized by a crown ether in dry dimethyl sulphoxide, initiated a free-radical chain oxidation of anionic 2-nitropropane. Superoxide dismutase, but not catalase, inhibited oxidation of the nitroalkane. Xanthine oxidase suffered a syncatalytic inactivation, during the co-oxidation of 2-nitropropane, which was reversed by dialysis. Cyanide exacerbated this syncatalytic inactivation and rendered it irreversible. The frequently observed oxidations of nitroalkanes by flavoenzymes now need to be re-examined to clarify the extent to which O2.--initiated free-radical chain oxidation contributed to the overall nitroalkane oxidation.

scholarly journals The mechanism of potentiation of horseradish peroxidase-catalysed oxidation of NADPH by porphyrins

1987 ◽  
Vol 242 (2) ◽  
pp. 611-613 ◽  
Author(s):  
J Van Steveninck ◽  
J P J Boegheim ◽  
T M A R Dubbelman ◽  
J Van der Zee
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Horseradish Peroxidase ◽  
Superoxide Radical ◽  
Experimental Results ◽  
Haematoporphyrin Derivative ◽  
Anaerobic Conditions ◽  
Catalysed Oxidation ◽  
Cytochrome C Reduction ◽  
Nadph Oxidation

Several porphyrins, including HpD (haematoporphyrin derivative), potentiate the oxidation of NADPH by horseradish peroxidase/H2O2. To elucidate the mechanism of potentiation, the following observations are relevant. During peroxidase-catalysed NADPH oxidation, O2-.(superoxide radical) is generated, as judged from superoxide dismutase-inhibitable cytochrome c reduction. This generation of O2-. is suppressed by HpD. Peroxidase-catalysed NADPH oxidation is stimulated by superoxide dismutase and by anaerobic conditions. Under anaerobic conditions HpD has no influence on peroxide-catalysed NADPH oxidation. Previous studies have shown that horseradish peroxidase is inhibited by O2-.. Thus the experimental results indicate that the potentiating effect of HpD can be explained by its ability to inhibit O2-. generation in the horseradish peroxidase/H2O2/NADPH system.

The pathophysiology of superoxide: roles in inflammation and ischemia

1982 ◽  
Vol 60 (11) ◽  
pp. 1346-1352 ◽  
Author(s):  
Joe M. McCord ◽  
Ranjan S. Roy
Keyword(s):  
Superoxide Dismutase ◽  
Xanthine Oxidase ◽  
Superoxide Radical ◽  
Tissue Injury ◽  
Xanthine Dehydrogenase ◽  
Chemotactic Factor ◽  
Calcium Transients ◽  
Acute Inflammatory Response ◽  
Superoxide Generation ◽  
Inflammatory Action

The superoxide radical plays major roles in the neutrophil-mediated acute inflammatory response and in postischemic tissue injury, although the sources and actions of the radical are quite different in these two pathological states. While neutrophils produce superoxide for the primary purpose of aiding in the killing of ingested microbes, a second useful function has evolved. The superoxide released from actively phagocytosing neutrophils serves to attract more neutrophils by reacting with, and activating, a latent chemotactic factor present in plasma. Superoxide dismutase, by preventing the activation of this superoxide-dependent chemotactic factor, exerts potent anti-inflammatory action. During ischemia, energy-starved tissues catabolize ATP to hypoxanthine. Calcium transients in these cells appear to activate a calmodulin regulated protease which attacks the enzyme xanthine dehydrogenase, converting it to a xanthine oxidase capable of superoxide generation. When the tissue is reperfused and reoxygenated, all the necessary components are present (xanthine oxidase, hypoxanthine, and oxygen) to produce a burst of superoxide which results in extensive tissue damage. Ischemic tissues are protected by superoxide dismutase or allupurinol, an inhibitor of xanthine oxidase.

Superoxide, Xanthine Oxidase and Platelet Reactions: Further Studies on Mechanisms by which Oxidants Influence Platelets

1981 ◽  
Vol 45 (03) ◽  
pp. 290-293 ◽  
Author(s):  
Peter H Levine ◽  
Danielle G Sladdin ◽  
Norman I Krinsky
Keyword(s):  
Superoxide Dismutase ◽  
Cytochrome C ◽  
Xanthine Oxidase ◽  
Direct Effect ◽  
Platelet Function ◽  
Experimental Conditions ◽  
Release Reaction

SummaryIn the course of studying the effects on platelets of the oxidant species superoxide (O- 2), Of was generated by the interaction of xanthine oxidase plus xanthine. Surprisingly, gel-filtered platelets, when exposed to xanthine oxidase in the absence of xanthine substrate, were found to generate superoxide (O- 2), as determined by the reduction of added cytochrome c and by the inhibition of this reduction in the presence of superoxide dismutase.In addition to generating Of, the xanthine oxidase-treated platelets display both aggregation and evidence of the release reaction. This xanthine oxidase induced aggreagtion is not inhibited by the addition of either superoxide dismutase or cytochrome c, suggesting that it is due to either a further metabolite of O- 2, or that O- 2 itself exerts no important direct effect on platelet function under these experimental conditions. The ability of Of to modulate platelet reactions in vivo or in vitro remains in doubt, and xanthine oxidase is an unsuitable source of O- 2 in platelet studies because of its own effects on platelets.

Effects of Greek legume plant extracts on xanthine oxidase, catalase and superoxide dismutase activities

2011 ◽  
Vol 68 (1) ◽  
pp. 37-45 ◽  
Author(s):  
Chrysoula I. Spanou ◽  
Aristidis S. Veskoukis ◽  
Dimitrios Stagos ◽  
Kalliopi Liadaki ◽  
Nectarios Aligiannis ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Xanthine Oxidase ◽  
Plant Extracts ◽  
Legume Plant

Hypothalamic superoxide dismutase, xanthine oxidase, nitric oxide, and malondialdehyde in rats fed with fish ω-3 fatty acids

2004 ◽  
Vol 28 (4) ◽  
pp. 693-698 ◽  
Author(s):  
Ahmet Songur ◽  
Mustafa Sarsilmaz ◽  
Sadik Sogut ◽  
Birsen Ozyurt ◽  
Huseyin Ozyurt ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Fatty Acids ◽  
Superoxide Dismutase ◽  
Xanthine Oxidase
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