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

---

Query: EC:1.17.3.2 (xanthine oxidase)
8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Electrochemical sensors based on immobilised cytochrome c or superoxide dismutase for the measurement of superoxide radical production by stimulated neutrophils are described. Cytochrome c was immobilised covalently at a surface-modified gold electrode and by passive adsorption to novel platinised activated carbon electrodes (PACE). The reoxidation of cytochrome c at the electrode surface upon reduction by superoxide was monitored using both xanthine/xanthine oxidase and stimulated neutrophils as sources of the free radical. In addition, bovine Cu/Zn superoxide dismutase was immobilised to PACE by passive adsorption and superoxide, generated by xanthine/xanthine oxidase, detected by oxidation of hydrogen peroxide produced by the enzymic dismutation of the superoxide radical. A biopsy needle probe electrode based on cytochrome c immobilised at PACE and suitable for continuous monitoring of free radical production was constructed and characterised.
...
PMID:Electrochemical sensors for direct reagentless measurement of superoxide production by human neutrophils. 133 38

The Onchocerca volvulus superoxide dismutase was expressed in Escherichia coli, using a protocol designed to produce the native enzyme rather than a fusion protein. The recombinant O. volvulus superoxide dismutase (rOVSOD) was found in the cytosol of the disrupted bacteria and represented > 10% of the total bacterial protein. The enzyme was purified to homogeneity using DEAE-Sepharose chromatography, followed by phenyl-Sepharose chromatography. The rOVSOD was enzymatically active which was demonstrated by its reactivity with O2.- produced either by the xanthine-xanthine oxidase system or by stimulated eosinophils. The specific activity was determined to be 4668 U mg-1. This activity could be blocked by rabbit antiserum raised against the rOVSOD. The maximal activity was obtained upon supplementation of the bacterial growth media and enzyme buffer with copper and zinc ions. Activity characteristics in the presence of inhibitors was also characteristic of a Cu/Zn superoxide dismutase. The rOVSOD has an apparent subunit molecular mass of 16,000 in SDS-PAGE. The active enzyme behaves as a dimer of 32 kDa as determined by gel filtration.
...
PMID:Characterization of enzymatically active Onchocerca volvulus Cu/Zn superoxide dismutase expressed in Escherichia coli. 783 82

This study examined the effects of inhibiting Cu/Zn superoxide dismutase with diethyldithiocarbamate (DETCA) on the ability of superoxide generating agents such as pyrogallol, hypoxanthine/xanthine oxidase and LY 83583, to influence NANC relaxation of strips of bovine retractor penis (BRP) muscle. Although pyrogallol (100 microM) and hypoxanthine (0.3 mM)/xanthine oxidase (64 mU ml-1) had little effect on NANC relaxation in control strips, both induced almost complete inhibition following treatment with DETCA (3 mM) for 1 h. Inhibition was due to the actions of superoxide anion since it was blocked by the addition of exogenous superoxide dismutase (250 U ml-1). LY 83583 (0.1-30 microM) produced a concentration-dependent inhibition of NANC relaxation even in control strips and this too was blocked by exogenous superoxide dismutase, but sensitivity to inhibition was enhanced 10-fold following treatment with DETCA. The data suggest that under normal circumstances the NANC neurotransmitter is protected by high levels of tissue superoxide dismutase, and inhibition of this enzyme increases its susceptibility to destruction by superoxide anions. An important impediment to accepting free nitric oxide as the NANC neurotransmitter in the BRP on the basis that superoxide anion-generating agents inhibit the actions of authentic nitric oxide but not those of NANC nerve stimulation has thus been removed.
...
PMID:NANC neurotransmission in the bovine retractor penis muscle is blocked by superoxide anion following inhibition of superoxide dismutase with diethyldithiocarbamate. 787 Feb 86

1. The effects of inhibiting endogenous Cu/Zn superoxide dismutase (SOD) with diethyldithiocarbamate (DETCA) were examined on the ability of hydroquinone, hydroxocobalamin and carboxy-PTIO to block nitrergic relaxation in the bovine retractor penis (BRP) muscle. 2. Incubation of strips of BRP with DETCA (3 mM) for 2 h reduced SOD activity from 73.1 +/- 15.7 to 8.2 +/- 1.9 units mg-1 protein. 3. Hydroquinone (10 microM--1 mM) produced weak inhibition of nitrergic (4 Hz, 10 s) relaxation in control strips of BRP, but powerful inhibition in strips treated with DETCA (3 mM, 2 h). Exogenous SOD (250 units ml--1) produced a partial blockade of the ability of hydroquinone to inhibit nitrergic relaxation in DETCA-treated strips. 4. In an assay of SOD-inhibitable reduction of cytochrome C, hypoxanthine (0.1 mM)/xanthine oxidase (16 munits ml-1) and pyrogallol (10 microM), led to the rapid generation of superoxide anion. Hydroquinone (10 microM) also led to the generation of the free radical, although the rate of generation was slower. 5. Two NO-scavenging agents, hydroxocobalamin (0.1 microM--1 mM) and carboxy-PTIO (0.1-1 mM), produced concentration-dependent blockade of nitrergic relaxation of the BRP. The magnitude of the blockade induced by these agents was unaffected following treatment with DETCA or SOD. 6. The findings with hydroquinone support our previous proposal that endogenous Cu/Zn SOD plays a vital role in protecting nitrergic neurotransmission from inactivation by superoxide anion. Results with hydroxocobalamin and carboxy-PTIO are consistent with the known ability of these agents to scavenge NO. The nitrergic neurotransmitter in the BRP thus appears to have the properties of NO.
...
PMID:Blockade of nitrergic transmission by hydroquinone, hydroxocobalamin and carboxy-PTIO in bovine retractor penis: role of superoxide anion. 873 70

A role of the oxygen radical generating system hypoxanthine-xanthine oxidase in hypoxia-reoxygenation injury was proposed 15 years ago. In recent years, however, new understanding of hypoxia-reoxygenation injury has been achieved and the significance of other oxygen radical generating systems has been acknowledged too. The hypothesis that an oxygen radical disease exists in preterm infants has recently been strengthened; an important observation is that preterm infants have lower activities of erythrocyte Cu/Zn superoxide dismutase compared to term babies. New actions of oxygen radicals have also been emphasized, and recently it has been demonstrated that the degree of protein oxidation of the lung of newborn infants is associated with chronic lung injury. The new insight into the interaction of oxygen radicals with other systems as excitatory amino acids and the NO system also increases the possibility to understand and hence prevent oxygen radical injury in the preterm infant as well as in adults exposed to an increased load of oxygen radicals.
...
PMID:Mechanisms of tissue injury by oxygen radicals: implications for neonatal disease. 883 70

1. The potential protective effect of several antioxidants [Cu/Zn superoxide dismutase (Cu/Zn SOD), ascorbate, reduced glutathione (GSH), and alpha-tocopherol (alpha-TOC)] on relaxations of the mouse anococcygeus muscle to nitric oxide (NO; 15 microM) and, where appropriate, nitrergic field stimulation (10 Hz; 10 s trains) was investigated. 2. The superoxide anion generating drug duroquinone (100 microM) reduced relaxations to exogenous NO by 54 +/- 6%; this inhibition was partially reversed by Cu/Zn SOD (250 u ml-1), and by ascorbate (500 microM). Following inhibition of endogenous Cu/Zn SOD activity with diethyldithiocarbamate (DETCA), duroquinone (50 microM) also reduced relaxations to nitrergic field stimulation (by 53 +/- 6%) and this effect was again reversed by Cu/Zn SOD and by ascorbate. Neither GSH (500 microM) nor alpha-TOC (400 microM) afforded any protection against duroquinone. 3. Xanthine (20 mu ml-1); xanthine oxidase (100 microM) inhibited NO-induced relaxations by 73 +/- 14%, but had no effect on those to nitrergic field stimulation, even after DETCA treatment. The inhibition of exogenous NO was reduced by Cu/Zn SOD (250 u ml-1) and ascorbate (400 microM), but was unaffected by GSH or alpha-TOC (both 400 microM). 4. Hydroquinone (100 microM) also inhibited relaxations to NO (by 52 +/- 10%), but not nitrergic stimulation. In this case, however, the inhibition was reversed by GSH (5-100 microM) and ascorbate (100-400 microM), although Cu/Zn SOD and alpha-TOC were ineffective. 5. 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO, 50 microM) inhibited NO-induced relaxations by 50 +/- 4%, but had no effect on nitrergic responses; the inhibition was reduced by ascorbate (2-200 microM) and alpha-TOC (10-200 microM), but not by Cu/Zn SOD or GSH. 6. Hydroxocobalamin (5-100 microM) inhibited, equally, relaxations to both NO (-logIC40 3.14 +/- 0.33) and nitrergic stimulation (-logIC40 3.17 +/- 0.22). 7. Thus, a number of physiological antioxidants protected NO from superoxide anions, and from direct NO-scavengers. The possibility that the presence of these antioxidants within nitrergically-innervated tissues might explain the lack of effect of the NO inhibitors on nerve-induced relaxation, without the need to invoke a transmitter other than free radical NO, is discussed.
...
PMID:Antioxidant protection of NO-induced relaxations of the mouse anococcygeus against inhibition by superoxide anions, hydroquinone and carboxy-PTIO. 888 31

To clarify whether the changes of free radicals and its scavengers are induced by thyroid disorders, we measured levels of free radical scavengers and checked O2 radical generating systems in the human thyroid gland. Thyroid specimens from patients with Graves' disease, follicular adenoma, and papillary and follicular carcinomas contained significantly higher concentrations of xanthine oxidase (XOD) and gluthathione peroxidase (GSH-PX), compared to those in the normal thyroid tissue. Catalase concentration was significantly lower in thyroid specimens from patients with Graves' disease and significantly lower in thyroid specimens from patients with follicular adenoma, compared to those in the normal thyroid tissue. Cu/Zn superoxide dismutase (Cu/Zn SOD) concentration was significantly lower in the specimens from follicular adenoma and papillary carcinoma and Mn SOD concentration was significantly higher in the specimens from papillary carcinoma than those in the normal thyroid tissue. The lipid peroxide concentration, expressed as malondialdehyde (MDA) concentration, was significantly higher in the specimens from papillary carcinoma than those in the normal thyroid tissue. These findings suggest that the levels of free radicals are increased and are scavenged and catalyzed in the thyroid of Graves' disease, whereas free radicals and lipid peroxide are not completely scavenged in papillary carcinoma tissues, suggesting that these substances affect some role in cell function of thyroid tumors.
...
PMID:Changes in free radical scavengers and lipid peroxide in thyroid glands of various thyroid disorders. 928 68

In this study bovine pulmonary artery endothelial cells (BPAEC) were used as a model system to investigate the effects of the hypoxanthine-xanthine oxidase (HXXO) oxygen radical donor system on ET-1 secretion into pulmonary vasculature. Incubation of BPAEC with HXXO for 4 h caused a significant reduction in ET-1 secretion, which was significantly offset by allopurinol or catalase, but not by Cu/Zn superoxide dismutase (SOD). ET-1 secretion was also reduced by H2O2, and this effect was again significantly offset by catalase. XO alone also reduced ET-1 secretion, but to a significantly lesser degree than did HXXO, and this effect was not offset by allopurinol, catalase, or SOD. None of the oxidant treatments were associated with a loss of immunoreactive ET-1 from endothelial cell medium containing synthetic peptide. The HXXO- and H2O2-mediated reductions in ET-1 secretion were accompanied by evidence of reduced cell viability. This loss of viability was absent when cells were treated with HXXO + catalase, allopurinol, or mercaptopropionyl glycine, but not when SOD was present. We conclude that under conditions of oxidative stress, the pulmonary vascular endothelium responds by secreting less ET-1. This may be relevant to its vasodilator functions in the pulmonary vasculature, which would therefore be compromised when the endothelium is exposed to oxidant stress.
...
PMID:Cytotoxicity-associated effects of reactive oxygen species on endothelin-1 secretion by pulmonary endothelial cells. 964 Dec 61

To determine the importance of different antioxidative enzymes for the defense status of insulin-producing cells, the effects of stable overexpression of glutathione peroxidase (Gpx), catalase (Cat), or Cu/Zn superoxide dismutase (SOD) in insulin-producing RINm5F cells on the cytotoxicity of hydrogen peroxide (H2O2), hypoxanthine/xanthine oxidase (H/XO), and menadione have been investigated. Single overexpression of Cat or Gpx provided less protection than the combined expression of Cat plus SOD or Cat plus Gpx, while single overexpression of SOD either had no effect on the toxicity of the test compounds or increased it. RINm5F cells were also susceptible to butylalloxan, a lipophilic alloxan derivative that is selectively toxic to pancreatic beta-cells. Overexpression of enzymes, both alone and in combination, did not protect against butylalloxan-induced toxicity while SOD overexpression increased it, as evident from a half maximally effective concentration (EC50) value. The addition of Cat to the culture medium completely prevented the toxic effects of H2O2 and H/XO but had no significant effect on the toxicity of menadione or butylalloxan. Extracellular SOD had no effect on the toxicity of any of the test compounds. The results of this study show the importance of a combination of antioxidant enzymes in protecting against the toxicity of reactive oxygen species. Thus, overexpression of Cat and Gpx, alone or in combination with SOD, by use of molecular biology techniques can protect insulin-producing cells against oxidative damage. This may represent a strategy to protect pancreatic beta-cells against destruction during the development of autoimmune diabetes and emphasizes the importance of optimal antioxidative enzyme equipment for protection against free radical-mediated diseases.
...
PMID:Complementary action of antioxidant enzymes in the protection of bioengineered insulin-producing RINm5F cells against the toxicity of reactive oxygen species. 975 95

1. In this study we investigated the ability of ascorbate to protect nitric oxide from destruction by superoxide anion. 2. Ascorbate produced concentration-dependent relaxation of rings of rat aorta, comprising two components: the first, seen at 1-300 microM, reached a maximum of 45.3+/-2.8%, and was abolished by endothelial removal or treatment with L-NAME (100 microM), demonstrating involvement of nitric oxide. The second occurred at concentrations of 1 mM and above and was associated with falls in the pH of the bathing fluid. 3. Pretreatment with ascorbate at concentrations up to 3 mM had no effect on the relaxation to acetylcholine (10 nM-10 microM) on endothelium-containing rings or adenosine (0.1 microM-3 mM) on endothelium-denuded rings. 4. An oxidant stress was applied to aortic rings, comprising inhibition of endogenous Cu/Zn superoxide dismutase by diethyldithiocarbamate (0.1 mM) followed by generation of superoxide anion by hypoxanthine (0.1 mM/xanthine oxidase (16 u ml(-1)). This reduced maximal acetylcholine-induced relaxation from 96.7+/-1.3% to 42.4+/-3.5% (P<0.001). Treatment with ascorbate (30 microM-3 mM) reversed this blockade in a concentration-dependent manner. 5. Our findings show that ascorbate has the ability to protect nitric oxide from destruction by superoxide anion. This action is seen with ascorbate at levels normally present in plasma, suggesting that this antioxidant may exert a tonic protective effect on nitric oxide within the vasculature.
...
PMID:Recovery by ascorbate of impaired nitric oxide-dependent relaxation resulting from oxidant stress in rat aorta. 983 15


1 2 Next >>

---