Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Mn(III)-salophen complex with superoxide scavenging activity was prepared from manganese(III) acetate dihydrate and salophen in ethanol. Visible absorption spectrum of the red-brown complex exhibits a shoulder at 430 nm which was absent with either salophen or manganic acetate alone. Titration of salophen with manganese(III) is consistent with a 1:1 Mn to salophen stoichiometry of the complex based on changes in the absorbance at 500 nm or of superoxide scavenging activity. The superoxide dismutase (SOD)-like activity of the complex in the xanthine-xanthine oxidase/cytochrome c assay was 1450 units/mg salophen. The SOD activity of the complex was suppressed 50% in the presence of EDTA (1 mM), but was not altered in the presence of bovine serum albumin (1 mg/ml) or crude protein extract of Escherichia coli QC779 sodA-sodB- (1 mg/ml). E. coli QC779 sodA-sodB- grew scantily after an 8-h lag phase in aerobic M63 glucose minimal medium. The aerobic growth of the E. coli SOD double mutant in glucose minimal medium was greatly enhanced in the presence of 5 or 10 microM Mn-salophen complex compared to that of control after 24 h incubation. Mn-desferal green complex (10 microM) and pink complex (5 microM) also increased growth rate of E. coli QC779 sodA-sodB- but to a lesser extent than Mn-salophen complex. However, the growth was completely inhibited by 50 microM Mn-salophen complex, 100 microM Mn-desferal green complex, or 10 microM Mn-desferal pink complex.
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PMID:Preparation and characterization of Mn-salophen complex with superoxide scavenging activity. 797 8

The formation of carbon centered free radicals, identified as methylcarbonyl species, was observed using ESR spectroscopy and the spin trapping agent 4-pyridyl-1-oxide-N-t-butyl nitrone (4-POBN) during the oxidation of acetaldehyde by xanthine oxidase. The reaction was dependent upon the presence of OH. radicals and was inhibited by the addition of superoxide dismutase, catalase or OH. radical scavengers. The generation of methylcarbonyl radicals was associated with a doubling of stable acetaldehyde adducts with serum albumin, and 4-POBN or superoxide dismutase and catalase, completely blocked this effect. Thus, methylcarbonyl radicals contributed to acetaldehyde-mediated protein alkylation which is involved in causing toxic as well as immunological reactions ascribed to acetaldehyde.
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PMID:Free radical activation of acetaldehyde and its role in protein alkylation. 802 86

Recent findings have suggested that nitric oxide (NO) reacts with superoxide anion (O2-) to form a potential oxidant, peroxynitrite anion, which then decays to hydroxyl radical and nitrogen dioxide. In order to ascertain this hypothesis in human polymorphonuclear leukocytes (PMNs) which release both NO and O2-, we studied oxidation of L-cysteine (CYS) and bovine serum albumin (BSA) by PMNs and cell-free O2(-)-generating system of hypoxanthine (HX)-xanthine oxidase (XO) reaction. Oxidation of CYS by HX-XO was equally inhibited by superoxide dismutase (SOD) and catalase (CAT), and that of BSA by HX-XO was inhibited weakly by SOD and strongly by CAT. PMNs stimulated with phorbol 12-myristate 13-acetate increased the oxidation rates of CYS and BSA, and they were inhibited by SOD and CAT almost in a similar way to those by HX-XO. The NO synthase inhibitor, NG-monomethyl-L-arginine (NMMA), was confirmed to have an inhibitory effect on the inhibition of platelet aggregation by PMNs, and L-arginine (ARG) reversed this effect. However, pretreatment of PMNs with either of NMMA, or ARG, or both did not change the oxidation rates of CYS and BSA. We could not confirm the hypothesis at least in human PMNs that interaction of NO with O2- forms powerful oxidants to sulfhydryls of CYS and BSA. These results suggest that oxidation of sulfhydryls of CYS and BSA by PMNs is primarily dependent on reactive oxygen species, and is not modified by NO production.
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PMID:Nitric oxide does not contribute to superoxide-mediated sulfhydryl oxidation in human polymorphonuclear leukocytes. 803 64

We quantitated the ability of intratracheally administered liposome-encapsulated antioxidant enzymes to reduce reactive oxygen species injury to the pulmonary microvasculature. Cationic liposomes containing 3,500 U of Cu,Zn superoxide dismutase (Cu,Zn SOD) and 3,124 U of catalase were instilled into rabbits. The animals were killed 2-72 h later and their lungs were removed and perfused with Krebs Ringer with 5% wt/vol of fat-free bovine serum albumin. The pulmonary filtration co-efficient (Kf,c) was measured before and after adding 500 microM xanthine and 5 mU/ml xanthine oxidase (XO) into the lung perfusate. Two hours after a single intratracheal instillation of liposome-entrapped Cu,Zn SOD and catalase, lung antioxidant enzyme activities were 34 and 125% higher than the corresponding control values, remained virtually unchanged for up to 8 h post-instillation, and then decreased, reaching baseline values between 24 and 72 h. Addition of xanthine and XO into the lung perfusate of un-instilled rabbits, or rabbits that received liposomes with inactivated enzymes, caused a 100% increase in Kf,c (control value: 2 +/- 0.12 ml.min-1 x cmH2O-1 per 100 g dry lung weight). On the other hand, Kf,c values of rabbits lungs instilled with liposome-encapsulated active Cu,Zn SOD and catalase and challenged with xanthine and XO 8-24 h later remained at baseline levels. Instillation of liposomes containing either enzyme was equally effective in preventing the increase in Kf,c, indicating that both superoxide anions and hydrogen peroxide were necessary for the initiation of injury. We concluded that intratracheal instillation of liposome-encapsulated antioxidant enzymes caused a transient increase of lung antioxidant enzyme levels which protects the pulmonary microvasculature from free radical-initiated injury.
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PMID:Mitigation of oxidant injury to lung microvasculature by intratracheal instillation of antioxidant enzymes. 823 68

Reactive oxygen radicals generated by mesangial cells or by resident or infiltrating macrophages may contribute to glomerular injury in glomerulonephritis. To determine whether superoxide anions have an effect on the glomerular barrier to macromolecules, we studied the responses of isolated glomeruli after exposure to superoxide generated by xanthine and xanthine oxidase or by activated macrophages. Glomerular volumetric responses to oncotic gradients of bovine serum albumin or an impermeant neutral dextran (mol wt 252 kd0 were used to calculate the albumin reflection coefficient (sigma albumin) and convectional permeability to albumin (1-sigma albumin) of control and superoxide-treated glomeruli. Albumin permeability of control glomeruli was not different from 0 (0.02 +/- 0.01, N = 50). After 10 minutes of exposure of glomeruli to superoxide generated by xanthine oxidase, albumin permeability was increased to 0.06 +/- 0.01 (N = 50). Albumin permeability did not increase further after incubations with xanthine and xanthine oxidase for up to 60 minutes. The increase in albumin permeability was prevented by superoxide dismutase (-0.02 +/- 0.01, N = 48) but was not affected by catalase or by indomethacin pretreatment. Coincubation of glomeruli with activated macrophages also increased albumin permeability to a maximum of 0.80 +/- 0.05 (N = 17). Albumin permeability was not increased by incubation of glomeruli with phorbol myristate acetate alone or with macrophages in the absence of phorbol myristate acetate. The effect of activated macrophages on albumin permeability, like that of superoxide generated chemically, was prevented by superoxide dismutase but not by catalase or indomethacin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of superoxide exposure on albumin permeability of isolated rat glomeruli. 838 94

The protective effect of N-acetylcysteine (NAC) against oxidant lung injury was investigated in a model of acute immunological alveolitis in the rat. Intrapulmonary immune complex deposition into rat lungs, induced by intratracheal infusion of immunoglobulin G (IgG) anti-bovine serum albumin (BSA) antibodies and intravenous injection of the antigen, caused lung damage associated with a marked decrease in [14C]5-hydroxytryptamine ([14C]5HT) uptake capacity, taken as a biochemical marker of endothelial cell function. The oral administration of a single dose of NAC (2 mmol.kg-1) 60 min before antigen/antibody (Ag/Ab) treatment was effective in preventing pulmonary endothelial cell [14C]5HT uptake loss induced by immune complex deposition. The mechanisms involved in this lung protective action of NAC were investigated by studying the antioxidant activity of NAC on hypoxanthine/xanthine oxidase-induced lung damage in vitro, and the effectiveness of the drug as lung glutathione (reduced form) (GSH) precursor in diethylmaleate-depleted rats. The results obtained provide further evidence on the ability of NAC to reduce the susceptibility of lung tissue to free radical-induced damage, by potentiating the antioxidant defence systems.
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PMID:Protection by N-acetylcysteine against pulmonary endothelial cell damage induced by oxidant injury. 847 21

Myeloperoxidase (MPO) is a lysosomal enzyme found in the primary granules of mammalian neutrophils. Together with MPO, peroxide and halide form a system of defense against bacteria. The present investigation was undertaken to study the bactericidal effects of the bovine-MPO/peroxide/halide system on pathogenic bacteria associated with bovine mastitis. We demonstrated that MPO together with oxidizing agents generated by xanthine oxidase, hypoxanthine and chloride form a potent antibacterial system against the common udder pathogens Staphylococcus aureus, Streptococcus uberis, Streptococcus agalactiae, Streptococcus dysgalactiae and Escherichia coli in a synthetic medium. However, when milk was added to the reaction mixture, the bactericidal properties of this enzyme system were completely inhibited. Loss of bactericidal activity in the milk-containing cultures was unable to be restored by increasing the concentration of MPO. Nor did an increase in concentrations of hypoxanthine and xanthine oxidase, or the replacement of the above-mentioned peroxidase generating system with a high concentration of hydrogen peroxide, significantly elevated the bactericidal activity that was inhibited by milk. The addition of bovine serum albumin to the synthetic medium reduced the bactericidal activity of the MPO/peroxide/chloride system in a dose-dependent manner. Therefore, milk proteins probably form adducts with strong bactericidal agents that are generated by the MPO system and thereby reduce the bactericidal potential of this system.
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PMID:Bactericidal activity of the bovine myeloperoxidase system against bacteria associated with mastitis. 856 Jul 39

Catalysis of the formation of reactive oxygen species (RO2S) by low molecular weight complexes of iron has been implicated in several pathological conditions in the retina since photoreceptors and retinal pigment epithelial cells are likely to be especially sensitive to RO2S. Since protective proteins cannot cross the blood-retinal barrier, it is likely that the retina performs its own protective functions by synthesizing proteins that bind iron and nonprotein iron complexes, the major catalysts of RO2S generation. Investigations were carried out to determine whether pigment epithelial cells are themselves sensitive to iron-generated RO2S and whether apo-transferrin and apo-hemopexin, known to be made locally in the retina, can perform a protective function. In 51Cr release assays, the toxicity of exogenous RO2S including hydrogen peroxide or superoxide (generated by xanthine oxidase/hypoxanthine) to human retinal pigment epithelial cells was inhibited by the iron chelators, desferrioxamine and apo-transferrin. Free but not protein-bound ferric iron and heme exacerbated the toxic effect. The toxic effect of heme was abolished by the heme-scavenging, extracellular antioxidant, apo-hemopexin, and also by exogenous bovine serum albumin. In addition, heme toxicity was inhibited by a 3 h preincubation of cells with either heme, apo-hemopexin, or heme-hemopexin 24 h prior to the toxicity assay. It is concluded, first, that toxic effects of iron and heme can be prevented by apo-transferrin or apo-hemopexin and, second, that exposure of RPE cells to free heme or hemopexin sets in motion a series of biochemical events resulting in protection against oxidative stress. It is probable that these include heme oxygenase induction.
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PMID:Heme-mediated reactive oxygen species toxicity to retinal pigment epithelial cells is reduced by hemopexin. 864 26

Tyrosinase isolated from cultured human melanoma cells was studied for tyrosine oxygenation activity. L-Tyrosine and D-tyrosine were used as substrates and dopa was measured with HPLC and electrochemical detection as the product of oxygenation. Incubations were performed in the presence or absence of dopamine as co-substrate. Oxygenation of L-tyrosine occurred only in the presence of dopamine as co-substrate. No oxygenation of D-tyrosine was found, and we conclude that human tyrosinase is characterised by exclusive specificity for the L-isomer of tyrosine in its oxygenase function. It has recently been suggested that superoxide anion is a preferential oxygen substrate for human tyrosinase. Incubations were therefore performed with L- and D-tyrosine, human tyrosine, and xanthine/xanthine oxidase in the system, generating superoxide anion and hydrogen peroxide. Considerable formation of dopa was observed, but the quantity was the same irrespective of whether D-tyrosine or L-tyrosine was used as the substrate. Furthermore, formation of dopa occurred in a xanthine/xanthine oxidase system when bovine serum albumin (BSA) was substituted for tyrosinase. Our results provide no evidence that superoxide anion is an oxygen substrate for human tyrosinase. In the incubate containing xanthine/xanthine oxidase, catalase completely inhibited dopa formation, and superoxide dismutase and mannitol each strongly inhibited dopa formation. The results are compatible with hydroxyl radicals being responsible for the formation of dopa, since such radicals may be secondarily formed in the presence of superoxide anion and hydrogen peroxide.
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PMID:Enzymatic and non-enzymatic oxygenation of tyrosine. 885 72

Increased vascular permeability to plasma proteins and altered hemodynamics at the site of inflammation are characteristics of inflammation. In the present study, alterations in endothelial barrier permeability were evaluated in different organs/tissues 6 h after a systemic inflammatory response induced by intravenous injection of bradykinin (BK; 1.7 mg/kg). The effect of intravenous pretreatment with indomethacin or ibuprofen (cyclooxygenase inhibitors), N-acetyl-L-cysteine (NAC, an oxygen free radical scavenger), and allopurinol (a xanthine oxidase inhibitor) was determined. Endothelial permeability was evaluated by determining tissue water content (TWC), 125I-labeled human serum albumin (HSA) flux, and albumin leakage index (ALI) in various organs/tissues. The vasodilation in the local tissues was reflected by tissue blood content (TBC), measured by 51Cr-labeled red blood cells. The results indicate that albumin flux significantly increased in the peritoneum, pancreas, stomach, PSI, DSI, colon, kidneys, liver, lungs, and brain, TBC significantly increased in the kidneys, liver, lungs, and heart, as well as in the intestine, and an increased ALI, assaying endothelial permeability considering local hemodynamic alterations was noted in the pancreas, kidneys, liver, lungs, PSI, and DSI in the group with BK alone. These changes were to varying degrees reversed by pretreatment with indomethacin, ibuprofen, N-acetyl-L-cysteine, or allopurinol, where the protective effect tended to be organ-dependent.
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PMID:Influence of anti-inflammatory and antioxidant agents on endothelial permeability alterations induced by bradykinin. 895 57


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