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

A new method for the determination of guanase is described. Xanthine, the product of the guanase reaction, is oxidized by xanthine oxidase, forming uric acid and hydrogen peroxide. Hydrogen peroxide is further reduced to water by catalase in the presence of ethanol. The acetaldehyde formed in this reaction step is dehydrogenated NAD or NADP dependent by aldehyde dehydrogenase. The NADH or NADPH production is measured and utilized for the calculation of the guanase activity. The sensitivity of the method can be doubled by the addition of uricase, which oxidizes uric acid to permit the formation of another mole of hydrogen peroxide.
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PMID:A new spectrophotometric assay for enzymes of purine metabolism. II. Determination of guanase activity. 48 57

Xanthine oxidase activity in milk was determined by measuring the rate of formation of vanillic acid from vanillin. Raw milk received at a dairy plant had .208 units xanthine oxidase activity per ml and after 24-h storage at 4 C, .228 units per ml. Upon further storage activity decreased. Heating the fresh raw milk in a water bath to 55 C increased xanthine oxidase activity to .236 units per ml. Partial inactivation of the enzyme occurred when milk was heated at 60, 65, or 70 C for 5 min, and destruction was almost complete with heat at 75 C for 5 min. Raw milk heated at 48 C for 5 min and homogenized at pressures between 70.3 and 281.2 kg/cm2 had xanthine oxidase activities which were a linear function of pressure and showed that each additional kg/cm2 pressure resulted in additional xanthine oxidase activity of .16 milliunits per ml of milk.
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PMID:Influence of storage, heat, and homogenization upon xanthine oxidase activity of milk. 64 Dec 38

The reactions of native bovine catalase with superoxide and solvated electrons have been investigated using three different methods for generation of these reducing substrates: gamma-radiolysis of oxygenated or deaerated buffer solutions in the presence of an OH radical scavenger; either xanthine or acetaldehyde with xanthine oxidase; and low-temperature (77 K) gamma-radiolysis of buffered ethylene glycol/water solutions with subsequent annealing of samples at 183 K. The first spectral evidence for catalase compound II formation from native catalase via reaction with superoxide was obtained. The results are compared with results for peroxidase compound II or III formation observed under the same experimental conditions. A scheme is proposed to explain these observations involving intermediate formation of catalase compounds I and III and the ferrous enzyme. The one-electron reduction of catalase and peroxidase by radiolytically-generated solvated electrons was compared. In the present study the first absorption spectrum of a high-spin ferrous catalase which has peaks at 561 and 594 nm is reported, in comparison with a hemochromogen low-spin ferrous peroxidase observed under the same experimental conditions (peaks at 527 and 556 nm). Both spectra were recorded at 77 K. Data presented in this work also provide the first spectral evidence indicating the low temperature (183 K) conversion of high-spin ferrous catalase into compound III (oxycatalase) in the presence of dioxygen. Under the same experimental conditions low-spin ferrous peroxidase was converted into the high-spin ferrous form without oxyperoxidase formation.
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PMID:Spectral studies of intermediate species formed in one-electron reactions of bovine liver catalase at room and low temperatures. A comparison with peroxidase reactions. 136 11

The antioxidative effect of three water-soluble components isolated from Salvia miltiorrhiza has been investigated. All the three components were found to inhibit both NADPH-vit C and Fe(2+)-cysteine induced lipid peroxidation (malondialdehyde formation) in rat brain, liver and kidney microsomes in vitro. The order of their inhibitory effect is as follows: salvianolic acid A, salvianolic acid B and rosmarinic acid. The inhibitory effect on lipid peroxidation induced by NADPH-Vit C was more than that induced by Fe(2+)-cysteine. In addition, the three compounds lowered the production of superoxide anion radical (O2-) in xanthine-xanthine oxidase system. The order of their potency was similar to that in antilipoperoxidation. The above results suggest that the three components have strong antilipoperoxidant activity in vitro, which may be partly through scavenging O2-..
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PMID:[Antioxidative effect of three water-soluble components isolated from Salvia miltiorrhiza in vitro]. 141 77

The protein-bound polysaccharide of Coriolus versicolor QUEL (PS-K) has been found to express antioxidant activity as an "ion-radical scavenger" in diamine oxidation reactions. The mode of this expression was examined to determine whether the drug functioned as a simple radical scavenger or mimicked the action of superoxide dismutase (SOD). The latter was confirmed in both enzymatic and nonenzymatic superoxide anion radical (O2-.) producing systems in vitro. The SOD mimetic activity of PS-K was demonstrated by quantitative analysis of hydrogen peroxide as the end product of O2-., its formation being assisted catalytically by SOD or PS-K. Analysis by electron spin resonance also confirmed the SOD mimetic activity of PS-K in a xanthine-xanthine oxidase reaction. Relative SOD activity with PS-K was approximately 1/8,000 in a KO2-O2-.-producing system. The SOD mimetic activity of PS-K resisted treatment by 0.7N HCl, 0.7N NaOH, boiling for 30 minutes in a double water bath, and digestion by pronase. Fractionation according to differences in molecular mass caused no significant increase in relative SOD activity within a certain range of molecular mass, indicating that there is no definite molecule expressing SOD mimetic activity. Tumor-bearing rats and human patients with digestive tract cancer who suffered from oxidative stress were relieved by a single intraperitoneal administration of PS-K or a 1-day peroral prescription.
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PMID:Mimicking of superoxide dismutase activity by protein-bound polysaccharide of Coriolus versicolor QUEL, and oxidative stress relief for cancer patients. 162 73

Ceruloplasmin (CP) effectively inhibited superoxide and ferritin-dependent peroxidation of phospholipid liposomes, using xanthine oxidase or gamma irradiation of water as sources of superoxide. In addition, CP inhibited superoxide-dependent mobilization of iron from ferritin, suggesting that CP inhibited lipid peroxidation by decreasing the availability of iron from ferritin. CP also exhibited some superoxide scavenging activity as evidenced by its inhibition of superoxide-dependent cytochrome c reduction. However, superoxide scavenging by CP did not quantitatively account for its inhibitory effects on iron release. The effects of CP on iron-catalyzed lipid peroxidation in systems containing exogenously added ferrous iron was also investigated. CP exhibited prooxidant and antioxidant effects; CP stimulated at lower concentrations, reached a maximum, and inhibited at higher concentrations. However, the addition of apoferritin inhibited CP and Fe(II)-catalyzed lipid peroxidation at all concentrations of CP. In addition, CP catalyzed the incorporation of Fe(II) into apoferritin. Collectively these data suggest that CP inhibits superoxide and ferritin-dependent lipid peroxidation via its ability to incorporate reductively-mobilized iron into ferritin.
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PMID:Effects of ceruloplasmin on superoxide-dependent iron release from ferritin and lipid peroxidation. 164 82

The excessive generation of free radicals is thought to be one of the major mechanisms leading to tissue injury in various pathological conditions, including ischemia, inflammation, and trauma. Conversion of xanthine dehydrogenase (XDH) to xanthine oxidase (XO) contributes to the formation of superoxide, an oxygen radical. We measured XDH and XO activity using a newly developed fluorometric assay in an experimental spinal cord injury model in rats. XO activity increased by more than 100% 4 h after spinal cord trauma. Total (XDH + XO) activity also increased by 96% during the same period. Allopurinol, an inhibitor of XO (100 mg/kg/day x 2 days, i.p.), completely inhibited plasma and spinal cord XO activity but did not affect posttraumatic edema determined by water content or polymorphonuclear (PMN) cell infiltration reflected by myeloperoxidase (MPO) activity in traumatized spinal cord. These results indicate that XDH conversion to XO may not be the major mechanism of oxygen radical formation in the pathogenesis of vasogenic edema or inflammatory response in this experimental spinal cord injury model in rats.
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PMID:Xanthine oxidase in experimental spinal cord injury. 164 10

The effects of alpha-tocopherol, ascorbic acid and rutin on peroxidative processes were studied in xanthine-xanthine oxidase system, linoleic acid ufasomes and human erythrocyte membranes. In these three systems, tested compounds scavenge superoxide anion radicals or inhibit lipid peroxidation in a concentration-dependent manner, and it was shown that rutin was the most potent radical scavenger, followed by ascorbic acid and alpha-tocopherol. An important antilipoperoxidant activity was observed when these compounds were tested in combination, demonstrating that a dose-dependent interaction occurs. Water-soluble (rutin and ascorbic acid) as well as lipid-soluble (tocopherol) antioxidants are involved in the protection of polyunsaturated fatty acids constituting the ufasome or erythrocyte ghosts. When these compounds are used in combination, an additive effect is observed with alpha-tocopherol and ascorbic acid or rutin, while a supra-additive effect (synergism) is noted with ascorbic acid and rutin. Results obtained with the triple combination alpha-tocopherol-ascorbic acid-rutin show that an increase in superoxide radical scavenging activities or in lipid peroxidation inhibition is possible after the addition of a third antioxidant, as compared with the protective effects produced by the double combination of these compounds. This interaction takes place not only in homogeneous aqueous solutions, but also in ufasome or erythrocyte ghost preparations. It is suggested that ascorbic acid and rutin interacts with tocopherol at the surface of or the interface with the membrane, and that rutin simultaneously interacts with ascorbic acid.
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PMID:Additional antilipoperoxidant activities of alpha-tocopherol and ascorbic acid on membrane-like systems are potentiated by rutin. 165 40

A quantitative structure-activity relationship for the reaction of xanthine oxidase with a homologous series of alpha, beta-unsaturated aldehydes, which are known to be products of lipid peroxidation, was investigated. Aldehydes in the series 2-butenal through 2-nonenal and 4-hydroxy-2-nonenal, displayed differential reactivity toward xanthine oxidase as measured by production of the superoxide radical anion. Kinetic parameters for the rate of superoxide production and substrate affinity were determined via the superoxide dismutase-sensitive reduction of cytochrome c. Trends in kinetic parameters as a function of carbon number for the series of trans-2-enals was consistent with a dependence on substrate hydrophobicity. Log kw', a hydrophobicity constant widely employed as a model for the octanol/water partition coefficient, was determined by reversed phase liquid chromatography for the alpha, beta-unsaturated aldehydes in this study. Linear relationships for the correlation of substrate binding (pKm) and efficiency of superoxide production (log kcat/Km) with substrate hydrophobicity (log kw') were found. The mode of inhibition of xanthine oxidation by 2-butenal is shown to be noncompetitive, suggesting distinct binding sites for purine and aldehydic substrates. It is suggested that the reaction of xanthine oxidase with unsaturated aldehydes could be an important route of amplification of oxidative damage in cells.
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PMID:The reaction of xanthine oxidase with aldehydic products of lipid peroxidation. 166 61

The effects of noxious stimuli and morphine on the serotonergic system in the nucleus raphe magnus were examined by in vivo voltammetry studies, using anesthetized rats. The normal electrochemical signal of 280-300 mV was essentially due to the presence of 5-hydroxyindoles in the nucleus raphe magnus. Heating or pinching produced mean decreases of 21.9 +/- 5.2% and 18.0 +/- 6.1% of control, respectively in the 5-hydroxyindole signal. Non-noxious (brushing or warm water) stimulation did not affect the 5-hydroxyindole signal. A small dose of morphine (0.5 mg/kg, i.p.) enhanced the inhibition of the signal by noxious stimuli but large doses (2.0 or 5.0 mg/kg, i.p.) resulted in lesser reductions of the signal. The value of the 5-hydroxyindole signal was unaffected by morphine alone (0.5, 2.0 and 5.0 mg/kg). Effects of both small- and large-doses of morphine were antagonized by naloxone (1 mg/kg, i.v.). Allopurinol (20 mg/kg, i.p.), a xanthine oxidase inhibitor, decreased the steady signal (40.7 +/- 16.2%). After pretreatment with allopurinol, noxious stimuli-induced decreases, both with and without administration of morphine, were similar to those in nontreated rats. In brief, noxious stimulation was found to decrease 5-hydroxyindole signal in the nucleus raphe magnus; morphine enhanced or attenuated this decrease in the anesthesized rat.
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PMID:Effects of morphine on the electrochemical signal modified by noxious stimuli in the nucleus raphe magnus of anesthetized rats. 177 23


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