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)

Crude cell-free extracts of nine strains of Streptomyces tested for nitroalkane-oxidizing activity showed production of nitrous acid from 2-nitropropane, 1-nitropropane, nitroethane, nitromethane, and 3-nitropropionic acid. These substrates were utilized in most strains but to a decreasing extent in the order given, and different strains varied in their relative efficiency of oxidation. p-Nitrobenzoic acid, p-aminobenzoic acid, enteromycin, and omega-nitro-l-arginine were not attacked. d-Amino acid oxidase, glucose oxidase, glutathione S-transferase, and xanthine oxidase, enzymes potentially responsible for the observed oxidations in crude cellfree extracts, were present at concentrations too low to play any significant role. A nitroalkane-oxidizing enzyme from streptozotocin-producing Streptomyces achromogenes subsp. streptozoticus was partially purified and characterized. It catalyzes the oxidative denitrification of 2-nitropropane as follows: 2CH(3)CH(NO(2))CH(3) + O(2) --> 2CH(3)COCH(3) + 2HNO(2). At the optimum pH of 7.5 of the enzyme, 2-nitropropane was as good a substrate as its sodium salt; t-nitrobutane was not a substrate. Whereas Tiron, oxine, and nitroxyl radical acted as potent inhibitors of this enzyme, superoxide dismutase was essentially without effect. Sodium peroxide abolished a lag phase in the progress curve of the enzyme and afforded stimulation, whereas sodium superoxide did not affect the reaction. Reducing agents, such as glutathione, reduced nicotinamide adenine dinucleotide, and nicotinamide adenine dinucleotide phosphate, reduced form, as well as thiol compounds, were strongly inhibitory, but cyanide had no effect. The S. achromogenes enzyme at the present stage of purification is similar in many respects to the enzyme 2-nitropropane dioxygenase from Hansenula mrakii. The possible involvement of the nitroalkane-oxidizing enzyme in the biosynthesis of antibiotics that contain a nitrogen-nitrogen bond is discussed.
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PMID:Nitroalkane oxidation by streptomycetes. 3 65

Milk fat globule membranes (MFGM) and rough endoplasmic reticulum (RER) membranes were isolated from milk and lactating mammary gland from the cow and were characterized by biochemical and electron microscope methods in terms of gross composition (proteins, phospholipids, neutral lipids, cholesterol, RNA, and DNA) and purity. Both fractions contained significant amounts of a b-type cytochrome with several properties similar to those of cytochrome b5 from liver, as well as a rotenone-insensitive NADH- and NADPH-cytochrome c reductase. The b-type cytochrome content in the apical plasma membrane-derived MFGM was of the same order of magnitude as it was in RER membranes. It was characterized by a high resistance to extraction by low- and high-salt concentrations and nonionic detergents. MFGM contained much more flavin and much higher activities of xanthine oxidase than the RER membranes. The same redox components were found in MFGM and mammary RER from women, rats, mice, and goats, but in absolute contents great differences between the species were noted. The cytochromes described here differed from liver cytochrome b5 in some spectral properties. The alpha-band of the reduced hepatic cytochrome b5 is asymmetric with a maximum at 555 nm that is split into two distinct peaks at low temperatures. The alpha-band of the b-type cytochromes from MFGM and mammary RER appears as one symmetrical peak at about 560 nm that is not split at low temperatures. When treated with cyanide, MFGM and mammary microsomes showed difference spectra of a reduced b-type cytochrome. Under the same conditions, liver microsomes gave a completely different spectrum. These findings demonstrate the presence of a b-type cytochrome and associated redox enzymes in MFGM, i.e., a derivative of the apical cell surface membrane that is regularly used for envelopment of the milk fat globule during secretion.
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PMID:Redox constituents in milk fat globule membranes and rough endoplasmic reticulum from lactating mammary gland. 85 33

A stable endothelium-derived relaxing factor has been reported to be generated on exposure of endothelial cells to the superoxide anion. In this study, we first evaluated the effects of the relaxing factor and cromakalim on mechanical tone and, second, assessed their consequences on the 86Rb efflux rate. On application of hypoxanthine-xanthine oxidase to a bath for generating superoxide anion, the precontracted rabbit mesenteric artery exhibited another transient increase in contraction, followed by sustained relaxation. This relaxation was lost in the K(+)-physiological salt solution (PSS) (greater than 35 mM) and was inhibited by glibenclamide (10 microM) but not by N-methyl-L-arginine or methylene blue. Hypoxanthine-xanthine oxidase application did not increase either basal or stimulated synthesis of guanosine 3',5'-cyclic monophosphate. In the presence of 2 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid and 10 mM MgCl2, the relaxing factor caused a significant increase in 86Rb efflux from the aortic and mesenteric arterial segments, as did the cromakalim. The increased 86Rb efflux, either by the relaxing factor or by cromakalim, was wholly inhibited by glibenclamide. These results suggest that superoxide-mediated endogenous relaxing factor may have a similar mechanism of action to cromakalim in vasodilatation.
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PMID:Similarities between effects of superoxide-mediated endothelium-derived relaxing factor and cromakalim. 131 29

The role of solution ionic strength in perhydroxyl (HOO.) and peroxyl (ROO.) radical initiated lipid peroxidation has been defined and investigated. Xanthine oxidase activity was used as the source of superoxide (O2-) and its conjugate acid (HOO.) in these experiments. While the enzyme's activity varied with changes in ionic strength, the effect could be factored out of the lipid peroxidation studies. Both HOO.- and ROO.-initiated peroxidations of linoleic acid were promoted by increases in solution ionic strength: the inclusion of 0.1 M of various alkali metal salts in the reaction resulted in up to a 4-fold increase in the overall peroxidation rate. Significant differences between alkali metal cations (Li+, Na+, K+, Cs+) and halogen anions (F-, Cl-, Br-) were not observed. Thus, the increased rates of lipid peroxidation were attributable to changes in solution ionic strength rather than specific ion-reaction interactions. Ionic stimulation of lipid peroxidation occurred only in the presence of preexisting fatty acid hydroperoxides (LOOHs), which provided additional support for the hydrogen atom transfer mechanism previously proposed [Aikens, J., and Dix, T. A. (1991) J. Biol. Chem. 266, 15091] for the HOO./LOOH initiation process. Physiologically appropriate salt concentrations were used in these studies, hence the results may have biological significance.
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PMID:Effect of solution ionic strength on lipid peroxidation initiation by the perhydroxyl (xanthine oxidase-derived) and peroxyl radicals. 132 38

Peroxisomes are subcellular respiratory organelles which contain catalase and H2O2-producing flavin oxidases as basic enzymatic constituents. These organelles have an essentially oxidative type of metabolism and have the potential to carry out different important metabolic pathways. In recent years the presence of different types of superoxide dismutase (SOD) have been demonstrated in peroxisomes from several plant species, and more recently the occurrence of SOD has been extended to peroxisomes from human and transformed yeast cells. A copper,zinc-containing SOD from plant peroxisomes has been purified and partially characterized. The production of hydroxyl and superoxide radicals has been studied in peroxisomes. There are two sites of O2- production in peroxisomes: (1) in the matrix, the generating system being xanthine oxidase; and (2) in peroxisomal membranes, dependent on reduced nicotinamide adenine dinucleotide (NADH), and the electron transport components of the peroxisomal membrane are possibly responsible. The generation of oxygen radicals in peroxisomes could have important effects on cellular metabolism. Diverse cellular implications of oxyradical metabolism in peroxisomes are discussed in relation to phenomena such as cell injury, peroxisomal genetic diseases, peroxisome proliferation and oxidative stress, metal and salt stress, catabolism of nucleic acids, senescence, and plant pathogenic processes.
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PMID:Metabolism of oxygen radicals in peroxisomes and cellular implications. 133 30

Azelaic acid is an aliphatic dicarboxylic acid (HOOC-(CH2)7-COOH) which has recently been shown to have some practical therapeutic applications in skin diseases of different etiologies. It possesses diverse biological activities and its mechanisms of action are still under investigation. Azelaic acid, as disodium salt (C(9)2Na), at concentrations from 0.05 mM to 1.0 mM is capable of inhibiting significantly the hydroxylation of 1-tyrosine to 1-DOPA due to hydroxylradicals (HO.) produced by Fenton reaction. Similarly C(9)2Na significantly inhibits the heterogeneous photocatalytic oxidation of toluene to cresols, and the peroxidation of arachidonic acid (C20:4,n6), due to HO. formed by dissolved oxygen in the presence of UV-irradiated semiconductor TiO2 (photo-Fenton type reaction). C(9)2Na decomposition and its by-products formation are quantifiable only at high HO. concentrations. On the contrary, C(9)2Na is not a scavenger of O2-. generated by xanthine-xanthine oxidase system. Under the same experimental conditions, mannitol behaves like C(9)2Na. These data indicate that HO. scavenging capacity of C(9)2Na in vitro, and represent a useful tool for further investigations on the mechanisms of action of azelaic acid in biological systems.
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PMID:Scavenging activity of azelaic acid on hydroxyl radicals "in vitro". 164 75

This paper describes a new approach to the histochemical demonstration of superoxide generation by pulmonary vascular endothelial cells using a supravital high manganese/diamine technique, in which nascent superoxide radicals induce formation of amber, osmiophilic polymers of diaminobenzidine (DAB), detectable by light or electron microscopy. Superoxide oxidizes Mn2+ ions to the Mn3+ valence state. In turn trivalent manganese readily initiates formation of the polymerized DAB reaction product. Isolated rat lungs were perfused in situ with bloodless, buffered high manganese/DAB salt solution via the pulmonary artery. The aortic root was ligated to minimize outflow from the left heart, so that perfusate shunted across pulmonary capillary endothelium, to fill the alveolar spaces and drain via the trachea. Lungs were perfused for 3 min with oxygen equilibrated buffer, with or without 60 min prior warm anoxia, induced by initial perfusion with argon sparged buffer. After aldehyde fixation and tissue processing DAB reaction product was detected on the inner, luminal surface of the vascular endothelium by both light and electron microscopy. Bronchi and epithelial cells never stained positively. The histochemical reaction was absent or markedly reduced in non-manganese treated or superoxide dismutase treated lungs, as well as in lungs perfused with calcium free buffer. The histochemical reaction was not prevented by the xanthine oxidase inhibitors allopurinol or methylene blue. The high manganese/diamine technique provides direct visual evidence of a calcium dependent mechanism by which pulmonary vascular endothelial cells can generate superoxide radicals.
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PMID:Endothelial superoxide production in buffer perfused rat lungs, demonstrated by a new histochemical technique. 165 43

Skin tumor promotion induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) was inhibited by a concurrent and topical application of phthalic acid mono-n-butyl ester cupric salt (PAMBCu) in CD-1 mice initiated with 7,12-dimethylbenz[a]anthracene. PAMBCu inhibited TPA-caused epidermal ornithine decarboxylase (ODC) induction and ear edema formation, i.e. skin inflammation. However, neither PAMBCu nor superoxide dismutase (SOD) inhibited TPA-caused ODC induction in primary cultured mouse epidermal cells. 7-Bromomethylbenz[a]anthracene (BrMBA) is known to be a non-TPA type of tumor promoting agent. Epidermal ODC induction and inflammation caused by BrMBA were not inhibited by a concurrent application of PAMBCu. When mice were topically treated twice with PAMBCu, i.e. concurrently with and 7 h after BrMBA treatment, BrMBA-caused ODC induction was markedly suppressed. The same dose regimen of PAMBCu, however, failed to inhibit tumor promotion and inflammation caused by BrMBA. PAMBCu showed SOD-mimetic activity in superoxide generating systems, i.e. xanthine-xanthine oxidase reaction and TPA-stimulated polymorphonuclear leukocytes (PMN). Mono-n-butyl phthalate, which lacks SOD-mimetic activity, failed to inhibit TPA-caused ODC induction and skin inflammation. Therefore, inhibition by PAMBCu of TPA-caused tumor promotion, epidermal ODC induction and inflammation may be attributable to its SOD-mimetic activity. The results also support the contention that a superoxide anion of non-epidermal cell origin, such as PMN and macrophages, plays a role (probably some enhancing role) in in vivo ODC induction and tumor promotion caused by TPA. Failure of PAMBCu to inhibit BrMBA-caused tumor promotion suggests that superoxide anion generation is not involved in the tumor promoting action of this agent and that the anti-tumor promoting action of PAMBCu is dependent on the nature of the tumor promoting agents.
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PMID:Anti-tumor promoting action of phthalic acid mono-n-butyl ester cupric salt, a biomimetic superoxide dismutase. 211 May 12

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.
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PMID:Effect of the new anti-allergic compound ethyl 2-(4'-carboxybenzamido)-4-propionamidobenzoate sodium salt on human neutrophil superoxide production. 216 Feb 41

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


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