Activities of xanthine oxidase

Friedl, H.P., Till, G.O., Ryan, U.S. and Ward, P.A. (1989). Mediator induced activation of xanthine oxidase in endothelial cells. FASEB. J. 3, 2512-2518. 

The source of free radicals is multiplied under these circumstances, arachidonic acid metabolism, activation of xanthine oxidase, perturbation of electron flow within the respiratory chain, and NOS activation. Structurally, excitotoxicity is generally described as a necrotic process involving initial swelling of the cell and of the endoplasmic reticulum, clumping of chromatin, followed by swelling of the... 

Nitric oxide is a physiological substrate for mammalian peroxidases [myeloperoxide (MPO), eosinophil peroxide, and lactoperoxide), which catalytically consume NO in the presence of hydrogen peroxide [60], On the other hand, NO does not affect the activity of xanthine oxidase while peroxynitrite inhibits it [61]. Nitric oxide suppresses the inactivation of CuZnSOD and NO synthase supposedly via the reaction with hydroxyl radicals [62,63]. On the other hand, SOD is able to modulate the nitrosation reactions of nitric oxide [64]. 

Zhang, Z., Naughton, D., Winyard, P. G., Benjamin, N., Blake, D. R., Symons, M. C. R., Generation of nitric oxide by a nitrite reductase activity of xanthine oxidase a potential pathway for nitric oxide formation in the absence of nitric oxide synthase activity. Biochem. Biophys. Res. Commun. 249 (1998), p. 767—772... 

Antitoxic effect. Sesame oil, adiministered to male Wistar rats, ameliorated hepatic and renal damage in a dose-dependent manner and increased survival in lipopolysaccha-ride-treated rats. It decreased lipid peroxide concentration in serum but not in liver and kidney. Serum nitrite production was unaffected by sesame oil ingestion, and the activity of xanthine oxidase was reduced in the lipopolysaccharide-challenged rats k Anti-tumor activity. Water extract of the dried seed, administered intragastrically to mice at a dose of 50 mg/animal daily for 5 days, was active on CA-Ehrlich-ascites, 18% increase in life-span. Intraperitoneal administration was active on Dalton s lyphoma and CA-Ehrlich-ascites, 19 and 39% increase in life-span, respectively ". Seed oil, administered to rats intraperito-neally with 1,2,5,6-dibenzanthracene or re-tene, was active on sarcoma ". 

Zikakis, J. P. and Wooters, S. C. 1980. Activity of xanthine oxidase in dairy products. 

Allopurinol (Zyloprim) reduces the synthesis of uric acid by inhibiting the activity of xanthine oxidase, according to the scheme shown in Figure 24.2. The reduction in the uric acid pool occurs slowly. Because xanthine and hypoxanthine are more soluble than uric acid, they are easily excreted. 

DPI, however, is not specific for any one flavoprotein, it is also known to inhibit neutrophil NADPH oxidase [66] and the NADH oxidase activity of xanthine oxidase [67]. It has additionally been reported to affect potassium and calcium currents in isolated pulmonary smooth muscle cells [68] and its use in organ based bioassays must be treated with caution. 

De novo synthesis is particularly active in the liver and placenta. Nonhepatic tissues (e.g., bone marrow) depend on preformed purines that are synthesized in the liver and transported by red blood cells. They are very effective in salvaging the purines and exhibit little or no activity of xanthine oxidase, which oxidizes free purines. 

The optical activity of xanthine oxidase has been described above (see Metalloproteins). 

Allopurinol reduces the synthesis of uric acid by inhibiting the activity of xanthine oxidase (Figure 18). The reduction in the... 

The xanthine oxidase inhibitor is the substance that inhibits the activity of xanthine oxidase, involved in purine metabolism. There are two kinds of xanthine oxidase inhibitors purine analogs and non-purine-related compounds. The first category includes allopurinol (5), oxypurinol (6), and tisopurine (7). The second group... 

Malabsorption of molybdenum. Activities of xanthine oxidase, sulfite oxidase and aldehyde oxidase are therefore deficient (see Molybdoenzymes). Urinary xanthine and uric acid high and low, respectively (see Purine degradation). Mental retardation, seizures, cerebral atrophy, lens dislocation. 

Sustained elevation of [Ca ji in ischaemia can promote the conversion of xanthine dehydrogenase to xanthine oxidase (McCord 1985). Under low energy conditions, where large parts of ATP are converted to hypoxanthine, this may result in a massive generation of reactive oxygen species. The activation of xanthine oxidase has been implicated for ischaemic neuronal death in vivo (Coyle and Putt-FARCKEN 1993) and in kainate toxicity to cerebellar granule cells in vitro (Dykens et al. 1987). 

Both normoxic and hypoxic bovine pulmonary microvascular endothelial cells constitutively released xanthine oxidase (EC 1.1.3.22) activity into their culture media (Partridge et al. 1992). Incubation of hypoxic or normoxic bovine pulmonary microvascular endothelial cells with oxygenated medium (95% O2) stimulated the release of xanthine oxidase activity into the extracellular medium within 5 min. The xanthine oxidase activity could not be detected in the oxygenated medium after 60 min incubation with 95 % Oj. Oestradiol (10 iM) almost completely inhibited xanthine oxidase and dehydrogenase activities in both normoxic and hypoxic rat pulmonary microvascular endothelial cells (Kayyali et al. 1999). Dexamethasone increased the activity of xanthine oxidase, and also induced xanthine oxidase promoter activation in... 

Xanthine oxidase can reduce nitrate to nitrite (Westerfield et al. 1959, Fridovich and Handler 1962). Xanthine oxidase and dissimilatory nitrate reductase share structural similarities. Both are molybdoenzymes and contain flavin adenine dinucleotide and Fe/S clusters (McCord 1985, Mitchell 1986, Payne et al. 1997). Zhang et al. (1998) reported that both purified bovine buttermilk xanthine oxidase and xanthine oxidase-containing inflamed human synovial tissue can generate NO by reducing nitrite in the presence of NADH. This nitrite reductase activity of xanthine oxidase may act as a supplement to the activity of nitric oxide synthase (NOS) to redistribute blood flow to ischaemic tissues when NOS activity is absent. 

There was no specific activity of xanthine oxidase in the duodenal mucosa in Cases 1, 3 and 4. 

The interpretation that molybdenum is required for any of the reactions of xanthine oxidase has been questioned by Westerfeld and associates, who consider that the only effect of molybdenum is to stimulate dehydrogenase activity of xanthine oxidase. 

ROS are increasingly being cited as agents of normal signal transduction, mid, while their source is usually uncertain, xanthine oxidase XO is often a likely candidate. A phorbol ester tumor promoter such as PMA enhances the generation of ROS accumulation and declines the ROS detoxification enzymes in both epidermal and inflammatory cells. It triggers ROS accumulation through activation of xanthine oxidase (XO) or the stimulation of PMNs which cause NADPH oxidase activation. 

Physiological and biochemical effects of PBE are, to date, not well studied PBE has been shown to inhibit platelet aggregation [13] and therefore proposed in venous insufficiency [14]. In 1999 some biochemical targets of PBE action were proposed, e.g., inhibition of the respiratory electron transport chain [15]. PBE also dose-dependently inhibited the activities of xanthine oxidase, xanthine dehydrogenase, horseradish peroxidase, and lipoxygenase [16]. Nardili and... 

Bazin MA, Le Lamer AC, Delcros JG et al (2008) Synthesis and cytotoxic activities of usnic acid derivatives. Bioorg Med Chem Lett 16 6860-6866 BeGora MD, Fahselt D (2001) Usnic acid and Atranorin concentrations in lichens in relation to bands of UV irradiance. Bryologist 104 134-140 Behera BC, Adawadkar B, Makhija U (2003) Inhibitory activity of xanthine oxidase and superoxide-scavenging activity in some taxa of the lichen family Graphidaceae. Phytomedicine 10 536-543... 

Behera BC, Adawadkar B, Makhija U (2003) Inhibitory activity of xanthine oxidase and superoxide-scavenging activity in some taxa of the lichen family Graphidaceae. Phytomedicine 10 536-543... 

The TPA-induced conversion of xanthine dehydrogenase to xanthine oxidase is reduced by curcumin to the basal level noted in untreated cells. Activity of xanthine oxidase is remarkably inhibited by curcumin in vitro but not by its structurally related compounds caffeic acids, chlorogenic acid and ferulic acid (37). When Colo205 colorectal carcinoma cells were treated with... 

From metabolic studies, an isotopic caffeine breath test has been developed that detects impaired liver function using the quantitative formation of labeled carbon dioxide as an index. From the urinary excretion of an acetylated uracil metabolite, human acet-ylator phenotype can be easily identified and the analysis of the ratio of the urinary concentrations of other metabolites represents a sensitive test to determine the hepatic enzymatic activities of xanthine oxidase and microsomal 3-methyl demethylation, 7-methyl demethylation, and 8-hydroxylation. Quantitative analyses of paraxanthine urinary metabolites may be used as a biomarker of caffeine intake. Fecal excretion is a minor elimination route, with recovery of only 2-5% of the ingested dose. 

Tatsumi, K., N. Koga, S. Kitamura, H. Yoshimura, P. Wardman, and Y. Kato. 1979. Enzymic cis-trans isomerization of nitrofiiran derivatives - isomerizing activity of xanthine oxidase, lipoyl dehydrogenase, DT-diaphorase and liver microsomes. Biochim. Biophys. Acta 567 75-87. 

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