Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The use of xanthine oxidase (XO) as a label in immunoanalysis has not been previously reported. This can be explained by the difficulties encountered in XO assays (poor sensitivity and versatility) and the competitive inhibition of the enzyme by allopurinol, a widely used hypouricemic agent. We demonstrate here that both difficulties can be circumvented. (i) The XO-dependent luminescent signal related to the oxidation of luminol is dramatically enhanced in the presence of iron-EDTA complex and sodium perborate in alkaline buffer. The mechanism of this enhancement is consistent with an O2-driven Fenton reaction, leading to the production of highly reactive OH radical. (ii) Residual inhibition of solid-phase bound XO by serum allopurinol and its metabolites is spontaneously reversible and can be prevented by the presence of folic acid or azahypoxanthine in the incubation buffer. With these two problems solved, XO can be classified as a choice label in immunoanalysis with the following properties: (i) high detection sensitivity (3 amol label), (ii) long-term luminescent signal (several days), (iii) versatile preparation and stability of conjugates, and (iv) long-term stability of the luminescence reagent. As an example of application, some data concerning total IgE and direct 17 beta-estradiol assays are described. Several other luminescent immunoassays of large and small molecules have been developed using XO conjugates as tracer (free and total T4, ultrasensitive thyroid stimulating hormone, CA 19.9, prolactin, hCG, specific IgE, anti-toxoplasma, and anti-chlamydia IgG), thus proving that XO can be classified as a universal label.
 ...
PMID:Application of a long-term enhanced xanthine oxidase-induced luminescence in solid-phase immunoassays. 211 11

A selective and sensitive assay of inosine, guanosine, hypoxanthine, guanine and xanthine by high-performance liquid chromatography with immobilized enzyme reactors was developed. The separation was achieved on a Capcell Pak C18 column (15 cm x 0.46 cm I.D.) with a mobile phase of 0.1 M phosphate buffer (pH 8.0) containing 7 mM sodium 1-hexanesulphonate and 0.1 mM p-hydroxyphenylacetic acid. The fluorimetric detection of hydrogen peroxide using immobilized peroxidase and p-hydroxyphenylacetic acid was applied to the assay of these compounds, which were oxidized to yield hydrogen peroxide in the presence of immobilized enzyme (purine nucleoside phosphorylase, guanase and xanthine oxidase). Enzyme reactions occurred sufficiently without post-column addition of reagents. Enzymes that catalysed the conversion of purine compounds were co-immobilized on aminopropyl controlled-pore glass packed in stainless-steel tubing. The detection limits were 30-200 pg per injection.
 ...
PMID:Determination of purine nucleosides and their bases by high-performance liquid chromatography using co-immobilized enzyme reactors. 211 20

The effect of 60 min of ischaemia on glomerular and tubular functions (osmolar clearance, fractional Na+ excretion, K+ clearance, concentrating ability) after different periods of time was studied in New Zealand White rabbits. Pronounced changes in both glomerular and tubular functions were observed immediately on reperfusion and after 48 h. One week after ischaemia the functions appeared to be normalized. Mannitol is routinely used in clinical kidney transplantation due to its hyperosmolar effects and its ability to scavenge the hydroxyl radical. In the present study the possible additive protective effect against ischaemia-reperfusion damage of a combined pretreatment with mannitol and oxygen free radical scavengers or mannitol and a xanthine oxidase inhibitor was examined. Oxypurinol was chosen as the xanthine oxidase inhibitor due to its direct inhibitory effect. Concerning glomerular function, no protective effect of the combined pretreatment compared with mannitol alone was observed. However, concerning the tubular function tests combined pretreatment with either mannitol-superoxide dismutase-catalase or mannitol-oxypurinol turned out to be superior compared with that of mannitol alone.
 ...
PMID:Protective effects of pretreatment with superoxide dismutase, catalase and oxypurinol on tubular damage caused by transient ischaemia. 212 35

Damage to the bases in DNA by the cupric ion-1,10-phenanthroline complex was investigated. Ten base products in DNA were identified and quantitated by the use of gas chromatography/mass spectrometry with selected-ion monitoring. DNA damage by the cupric ion-1,10-phenanthroline complex required the presence of a reducing agent such as ascorbic acid or mercaptoethanol. Products identified were typical hydroxyl radical induced products from the pyrimidines and purines in DNA, well-known from previous studies using various hydroxyl radical producing systems such as ionizing radiation, hypoxanthine/xanthine oxidase, or hydrogen peroxide in the presence of transition metal ions. Product formation was not significantly inhibited by typical scavengers of hydroxyl radical such as mannitol and sodium formate, but there was partial inhibition by dimethyl sulfoxide. Catalase substantially decreased formation of base products, and added hydrogen peroxide stimulated it, indicating the hydrogen peroxide dependency of DNA base damage. Superoxide dismutase afforded only a partial reduction in product yields in systems containing ascorbic acid. On the basis of the types of base products formed, the hydrogen peroxide dependency of product formation, and a previous report suggesting that DNA damage is due to a diffusible species [Williams, L. D., Thivierge, J., & Goldberg, I. H. (1988) Nucleic Acids Res. 16, 11607-11615], we propose that DNA base damage is caused by hydroxyl radical.
 ...
PMID:Modification of bases in DNA by copper ion-1,10-phenanthroline complexes. 212 17

Isoelectric variants of Cu,Zn-superoxide dismutase (Cu,Zn-SOD) have been reported to exist in various organs including rat liver. To elucidate the biochemical characteristics of the variants, rat liver Cu,Zn-SOD was purified and isolated into eight variants, i.e., pI 5.15, 4.88, 4.80, 4.75, 4.70, 4.65, 4.60, and 4.50. The pI 4.88 variant had the highest specific activity (4245 U/mg protein) and the highest yield (45% of original activity). The descending order of specific activity for the other variants was pI 4.80, 4.75, 5.15, 4.70, 4.65, 4.60, and 4.50. The specific activity correlated well with metal content. The specific activity for most variants was 5-9 times greater when determined at pH 10.0 than at pH 7.8. However, three preparations of pI 4.80 and 4.70 variants had 13.9-16.3 times greater specific activity at pH 10.0 versus 7.8, while one of the pI 4.60 variants was only 3.5 times greater. The rate of Coomasie brilliant blue G-250 binding was lowest with pI 4.88 followed by pIs 4.80 and 4.75. To evaluate the mechanisms which might produce these variants, the pI 4.88 variant was incubated with xanthine-xanthine oxidase or a mixture of rat liver microsome, NADPH, and sodium azide, and a shift to variants pI 4.80 and pI 4.75 was found. The shift was greatly inhibited by the presence of mannitol or by the omitting of azide, respectively. The existence of these variants was also confirmed by other methods: (i) direct application of rat liver 105,000g supernatant to an isoelectric focusing, and (ii) extraction of SOD from acetone powder prepared from rat liver homogenate. Results indicate that several variants most likely arise in tissue as a result of activated oxygen radical modification of variant pI 4.88.
 ...
PMID:Multiple isoelectric variants of copper, zinc-superoxide dismutase from rat liver. 214 34

Myofibrils from rat hearts were prepared in conditions maintaining their redox state, and their sulfhydryl groups were measured using a solution of urea and sodium dodecyl sulfate (SDS) as denaturant. The sulfhydryl content was 92 n mol/mg of protein, indicating that cysteins are in reduced form. In the presence of superoxide radicals generated in vitro with purine and xanthine oxidase, the myofibrillar sulfhydryl groups were oxidized.
 ...
PMID:[Assay of sulfhydryl groups in cardiac myofibrillar proteins: effect of oxygen radicals in vitro]. 215 Jul 78

The effect of the new orally active antiallergic compound ethyl 2-(4'-carboxybenzamido)-4-propionamidobenzoate sodium salt (AM-682) and its main metabolite (met-A) were evaluated on respiratory burst in isolated human polymorphonuclear neutrophils (PMN). Both compounds exhibited inhibitory effect with concentration dependency on the n-formyl-methionyl-leucyl-phenylalanine (FMLP)-induced superoxide (O-2) production by human PMN. The inhibitory activity of met-A (IC50 1.1 mumol/l) was higher than that of AM-682 (IC50 85 mumol/l). By contrast, these compounds affected neither PMN O-2 production induced by phorbol 12-myristate 13-acetate (PMA) nor extracellular O-2 generation by the reaction of xanthine oxidase with hypoxanthine. These results indicate that the effects of these compounds act specifically on the generation of O-2 and is not simply a scavenger of O-2. This anti-inflammatory effect may also be beneficial in the treatment of asthma.
 ...
PMID:Effect of the new anti-allergic compound ethyl 2-(4'-carboxybenzamido)-4-propionamidobenzoate sodium salt on human neutrophil superoxide production. 216 Feb 41

Isolated myocytes of rat heart, and sealed sarcolemmal vesicles of bovine heart, were used to examine the selectivity of the effects of partially reduced oxygen species (generated by a mixture of xanthine and xanthine oxidase) on cardiac sodium pump and several other ion transporters of the plasma membrane. When myocytes were exposed to xanthine plus xanthine oxidase, there were time-dependent inhibitions of ouabain-sensitive 86Rb+ uptake and (Na+ + K+)-ATPase activity that could be prevented by allopurinol, or by catalase and superoxide dismutase; suggesting the involvements of H2O2 or oxygen free radicals in the inhibition of the pump. This inhibition preceded any significant decrease in cellular ATP or in the number of viable cells. While ouabain increased 45Ca2+ uptake by myocytes as expected, exposure to xanthine plus xanthine oxidase decreased 45Ca2+ uptake; suggesting that the Na+, Ca2(+)-exchanger of the intact myocytes is also inhibited by oxygen metabolites. Simultaneous inhibitions of the pump, the Na+, Ca2(+)-exchange, the Na+, H(+)-exchange, and the Na+, Pi-cotransport activities also occurred in sarcolemmal vesicles that were treated with xanthine plus xanthine oxidase. These findings indicate that inactivations of the sodium pump and other sarcolemmal ion carriers are early events in the oxidant-induced damage to the cardiomyocyte. In the rat heart myocytes, a fraction of (Na+ + K+)-ATPase that seems to be more sensitive to ouabain, was inactivated more rapidly upon exposure of myocytes to xanthine plus xanthine oxidase; raising the possibility of the existence of different pump populations with different sensitivities to extracellularly generated oxygen metabolites.
 ...
PMID:Studies on the specificity of the effects of oxygen metabolites on cardiac sodium pump. 217 59

We made use of the xanthine oxidase inhibitor allopurinol and examined changes related to myocardial injury of the rat heart during hypoxia-re-oxygenation. The rat heart was perfused using the Langendorff method. With low-oxygen perfusion for 60 min in a solution saturated with mixed gases of 95% N2 + 5%O2, contractile tension did not develop and tension development was not restored upon re-oxygenation. During hypoxia, the resting tension increased (4.1 g) in the absence of allopurinol. In the allopurinol-administered group (100 microM), contractile tension did not develop during hypoxia; however, the development of tension was restored (18%) upon re-oxygenation. The elevation of resting tension was less (3.2 g) during hypoxia. All events related to the myocardial injury (inhibition of Na+, K(+)-ATPase activities, generation of malondialdehyde, extracellular leakage of creatine kinase) after low-oxygen perfusion for 60 min and re-oxygenating perfusion for 30 min were mild in the allopurinol treated group, compared with findings in the non-administered group. Tissue ATP at 10 min after low-oxygen perfusion was of a significantly high value in the allopurinol treated group (13.2 mumols/g dry weight), compared with findings in the group not given the drug (8.4 mumol/g dry weight). Sixty minutes after low-oxygen perfusion, tissue ATP in the allopurinol group also remained high, compared with the group not given the drug. Although the intensity of the epicardial NADH fluorescence indicated that the extent of inhibition of aerobic energy production during 10 min of low-oxygen perfusion was the same for both groups, lactate was produced in large quantities in the allopurinol treated group, hence energy generation advanced with glycolysis. These observations suggest that allopurinol prevents myocardial injury as a result of hypoxia-re-oxygenation. In the low-oxygen perfusion period, generation of energy is maintained and improved with glycolysis and there is a reduction in the generation of free radicals and an inhibition in lipid peroxidation.
 ...
PMID:Does allopurinol prevent myocardial injury as a result of hypoxia-re-oxygenation in rats? 220 93

Xanthine oxidase (XO) has been implicated as a source of free radicals mediating ischemia-reperfusion injury. Conversion of the non-free radical generating xanthine dehydrogenase (XD) to the free radical producing XO during ischemia has been demonstrated in several tissues. We examined the irreversible conversion of XD to XO in the dog brain after ischemia and after ischemia and reperfusion. Under pentobarbital sodium anesthesia and by use of a cerebrospinal fluid compression model of global cerebral ischemia, dogs were subjected to 30 min of ischemia (n = 8) or 30 min of ischemia and 60 min of reperfusion (n = 8). A cerebral perfusion pressure of 60 mmHg was maintained during reperfusion. Eight control dogs were not subjected to ischemia. After the dogs were killed their brains were rapidly removed and frozen in liquid nitrogen. XO and XD + XO activities were measured with a radioassay utilizing 8-[14C]hypoxanthine and separating substrate and products by thin-layer chromatography. Total XD + XO activity was significantly (P less than 0.05) decreased after ischemia and reperfusion (35.6 +/- 8.0 vs. 60.8 +/- 20.8 nmol.min-1.g protein-1 in controls, means +/- SD) but not after ischemia alone (48.2 +/- 20.4). XO/(XD + XO) was approximately 20% in all three groups. Irreversible XD to XO conversion is not an important mechanism leading to early tissue injury in global cerebral ischemia.
 ...
PMID:No conversion of xanthine dehydrogenase to oxidase in canine cerebral ischemia. 226 Jun 92


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>