Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pulse radiolysis studies show that the spin trap 3,5,dibromo-4-nitrosobenzene sulphonate (I) reacts rapidly with O2.- but the product formed is very unstable. No radicals were detected in ESR studies of solutions of I after reaction with O2.- formed by gamma-radiolysis. Evidence is presented that the stable radical observed by some, but not all workers, following exposure of I to the O2.(-)-generating xanthine/xanthine oxidase system, is produced by a peroxidatic oxidation using hydrogen peroxide formed by O2-. dismutation and that formation of this radical depends on the presence of peroxidase activity in the xanthine oxidase sample employed.
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PMID:Does 3,5,dibromo-4-nitrosobenzene sulphonate spin trap superoxide radicals? 215 21

Using analogous models of acute dermal vasculitis and alveolitis in rats, we have examined the role of oxygen-derived metabolities in the tissue damage associated with neutrophil influx into sites of immune complex deposition. In the lung, as previously reported, catalase and deferoxamine are highly protective, while superoxide dismutase (SOD) has a transient protective effect. The xanthine oxidase inhibitors, allopurinol, and lodoxamide, are also protective. In the skin, neither catalase (which has been covalently linked to the antibody) nor deferoxamine is protective, suggesting that H2O2 and iron are not absolutely required for the development of dermal vasculitis. In the skin, SOD, as well as the inhibitors of xanthine oxidase, have protective effects. These data suggest that the neutrophil-mediated pathways of immune complex injury in the dermal and pulmonary microvascular compartments are fundamentally different. As a measurement of neutrophil accumulation, measurements of myeloperoxidase in tissue extracts have been employed. In both the lung and skin, the protective effects of SOD and the xanthine oxidase inhibitors are paralleled by reductions in neutrophil influx into sites of injury. In contrast, catalase and deferoxamine have no effect on neutrophil accumulation. These data suggest that vascular beds in rat skin and lung are fundamentally different with respect to mechanisms of acute immune complex mediated injury. The data also provide evidence that O2- contributes significantly to the accumulation of neutrophils.
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PMID:Role of O2- in neutrophil recruitment into sites of dermal and pulmonary vasculitis. 215 35

The ability of various reactive oxygen species and serine proteases to activate latent collagenase (matrix metalloproteinase-1) purified from human neutrophils was examined. Latent 70-75 kD human neutrophil collagenase (HNC) was efficiently activated by known non-proteolytic activators phenylmercuric chloride (an organomercurial compound) and gold thioglucose (Au(I)-salt). Corresponding degree of activation was achieved by reactive oxygen species including hypochlorous acid (HOCl), hydrogen peroxide (H2O2) and hydroxyl radical generated by hypoxanthine/xanthine oxidase (HX/XAO). The presence of trace amounts of iron and EDTA were necessary and even enhanced H2O2 induced activation of latent HNC. This activation could be abolished by an iron chelator desferrioxamine and a hydroxyl radical scavenger mannitol. HOCl induced activation of latent HNC was not affected by desferrioxamine and mannitol. Thus, these compounds do not inhibit the active/activated form of HNC. Latent HNC could also be activated by trypsin and chymotrypsin but not by plasmin and plasma kallikrein. The ability of mannitol and desferrioxamine to inhibit the H2O2-induced activation of HNC suggests the transition metal dependent Fenton reaction to be responsible for localized and/or site-specific generation of hydroxyl radical/hydroxyl radical -like oxidants to act as the activating oxygen species. Our results support the ability of myeloperoxidase derived HOCl to act as a direct oxidative activator of HNC and further suggest the existence of a new/alternative oxidative activation pathway of HNC involving hydroxyl radical.
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PMID:Activation of latent human neutrophil collagenase by reactive oxygen species and serine proteases. 217 13

Present work describes a new property of HDL to act as a scavenger of O2- free radicals in vitro. This lipoprotein prevents both enzymic and non-enzymic generation of O2- anions as evidenced by inhibition of xanthine oxidase, peroxidase, peroxidation of pyrogallol and phenazine methosulphate-NADH reaction. Ascorbate stimulated MDA formation in microsomes has been shown to be suppressed by HDL and these effects are comparable with that of BHA.
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PMID:High density lipoprotein is a scavenger of superoxide anions. 217 36

The enzymatic N-hydroxylation of the purine base adenine to the genotoxic and mutagenic compound 6-N-hydroxylaminopurine is reported for the first time. Adenine was N-oxygenated in vitro by aerobic incubations with 3-methylcholanthrene or isosafrole induced microsomal fractions of rat liver homogenates and NADPH. The formation of 6-N-hydroxylaminopurine in the incubation mixtures under widely differing conditions was assayed using newly-developed, high-performance liquid- and thin-layer chromatographic methods. Optimal reaction conditions and kinetic parameters were determined. Neither superoxide anion nor hydrogen peroxide was directly involved in the N-hydroxylation reaction. Oxidases like xanthine oxidase and peroxidase (in the presence of hydrogen peroxide) did not catalyse this N-hydroxylation. The involvement of cytochrome P-450 isoenzymes in this reaction is supported by the observation that the N-hydroxylation is only observed after pretreatment of the rats with 3-methylcholanthrene or isosafrole. Other inducers (phenobarbital, ethanol, 5-pregnen-3 beta ol-20-one-16 alpha-carbonitrile) were without effect. This is the first example of the microsomal transformation of an endogenous substance to a toxic derivative by usually foreign substances (xenobiotics) metabolizing cytochrome P-450 isoenzymes. The significance for the in vivo situation is discussed on the basis of the data obtained in this study.
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PMID:Hepatic microsomal N-hydroxylation of adenine to 6-N-hydroxylaminopurine. 231 Apr 18

Acetylcholine and ATP are costored and coreleased during synaptic activity at the electric organ of Torpedo. It has been suggested that released ATP is converted to adenosine at the synaptic cleft, and in turn this nucleoside would depress the evoked release of acetylcholine. In the present communication we have used a chemiluminescent reaction that let us to monitor continuously the presence of adenosine in this preparation. The chemiluminescent reaction is based on the conversion of adenosine into uric acid and H2O2 by adenosine deaminase, nucleoside phosphorylase, and xanthine oxidase enzymes. The hydrogen peroxide has been detected by peroxidase-luminol mixture. The reaction has a sensitivity on the picomol range and discerned between Adenosine, AMP, ADP, and ATP. We have developed this technique in the hope of understanding whether adenosine is released during synaptic activity or it comes from the released ATP. We have studied the release or formation of adenosine in fragments of the electric organ and in isolated cholinergic nerve terminals obtained from it. In both conditions we have followed the effect of potassium stimulation upon the detection of adenosine. Potassium stimulation increased the extracellular adenosine either in slices or the synaptosomal fraction of Torpedo electric organ. The presence of alpha, beta-methylene ADP, an inhibitor of 5'-nucleotidase, inhibits the detection of adenosine, suggesting that extracellular adenosine is a consequence of ectocellular dephosphorylation of released ATP.
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PMID:The release of adenosine at the electric organ of Torpedo. A study using a continuous chemiluminescent method. 232 27

A new colorimetric procedure for the determination of purine nucleoside phosphorylase (PNP, E.C. 2.4.2.1) activity is described. In this procedure, the hydrogen peroxide formed in the PNP-xanthine oxidase reaction is used to oxidize the chromogenic reagents--3,5-dichloro-2-hydroxybenzenesulfonic acid/4-aminophenazone using the enzyme peroxidase. The rate of enzyme reaction is followed at 520 nm. This procedure correlated well with the UV method (290 nm), with a correlation coefficient of 0.98 (P less than 0.005). Within-run and between-run precision (CV) were less than 2.8% and 3.7%, respectively. Here we also describe an optimized NAD-dependent method (340 nm) for PNP determination. The colorimetric method is superior to both the 340 nm and the UV methods in terms of both sensitivity and precision. The mean erythrocyte PNP activity for 17 healthy subjects was 11.88 U/mL packed cells for the NAD-dependent method and 13.22 U/mL packed cells for the colorimetric method.
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PMID:A new colorimetric assay for purine nucleoside phosphorylase. 250 13

A wide range of luminescent assays for enzyme labels has been developed. The clinical application of luminescent assays for horseradish peroxidase, alkaline phosphatase, xanthine oxidase, beta-D galactosidase, and glucose 6-phosphate dehydrogenase is discussed. The enzyme luminescent methods provide improved sensitivity compared with colorimetric and fluorimetric assays. A new reagent, dioxetane phosphate, has provided a simple and extremely sensitive assay for alkaline phosphatase. The available instruments and new photographic detection techniques for luminescent assays are briefly discussed.
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PMID:Clinical applications of luminescent assays for enzymes and enzyme labels. 250 54

In this study the role of free radicals, lipid peroxidation, and neutrophil infiltration as mediators of ischemia and reperfusion-induced intestinal mucosal damage were investigated. We used a rat experimental model in which a ligated loop of the distal ileum was subjected to ischemia and reperfusion and the ensuing mucosal damage was assessed by means of lysosomal enzyme release and intestinal permeability measurements. We also determined the mucosal content of malondialdehyde, a lipid peroxidation product, and the mucosal activity of myeloperoxidase, a neutrophil granulocyte marker. Ischemia and revascularization alone caused increased mucosal permeability to sodium fluorescein, increased N-acetyl-beta-glucosaminidase release from the mucosa into the lumen, increased malondialdehyde content in the mucosa, and increased myeloperoxidase activity in the mucosa. Intravenous injection of enzymatic antioxidant, superoxide dismutase, together with xanthine oxidase inhibitor, allopurinol, prevented the malondialdehyde accumulation and caused attenuation of all the other effects of ischemia. Intravenous pretreatment of hydrocortisone sodium succinate (Solu-Cortef), a steroid and also a nonenzymatic antioxidant, prevented not only malondialdehyde accumulation but also neutrophil infiltration and mucosal damage. These data support a concept that neutrophil infiltration is an important element in ischemic mucosal damage. In addition, the blocking of this phenomenon may have clinical significance in attempts to modulate the potential damaging effects of the increased neutrophil infiltration associated with small-intestinal ischemia.
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PMID:Oxygen radicals, lipid peroxidation, and neutrophil infiltration after small-intestinal ischemia and reperfusion. 253 52

The formation and decay of intermediate compounds of horseradish peroxidase, lactoperoxidase, and myeloperoxidase formed in the presence of the superoxide/hydrogen peroxide-generating xanthine/xanthine oxidase system has been studied by observation of spectral changes in both the Soret and visible spectral regions and both on millisecond and second time scales. It is tentatively concluded that in all cases compound III is formed in a two-step reaction of native enzyme with superoxide. The presence of superoxide dismutase completely inhibited compound III formation; the presence of catalase had no effect on the process. Spectral data which indicate differences in the decay of horseradish peroxidase compound III back to the native state in comparison with compounds III of lactoperoxidase and myeloperoxidase are also presented.
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PMID:The reactions of horseradish peroxidase, lactoperoxidase, and myeloperoxidase with enzymatically generated superoxide. 254 42


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