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)

Copper (Cu2+) ions at physiological concentrations can promote the formation of hydroxyl radical (OH) or a species of equivalent reactivity. The reaction requires H2O2 and a reducing agent. Reduction of Cu2+ can be achieved by superoxide ion generated by a mixture of hypoxanthine and xanthine oxidase or added directly as its potassium salt. Reduction of Cu2+ can also be achieved by ascorbic acid. Hence both O2- -dependent and ascorbate-dependent formation of OH from H2O2 in the presence of Cu2+ can be observed. Only the former reaction is significantly inhibited by superoxide dismutase. The binding of Cu2+ to histidine or albumin at physiological concentrations decreases the formation of OH radicals in free solution in the presence of either ascorbate or an (O2- -generating system. It is suggested that OH is still formed but reacts immediately with the binding molecule.
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PMID:Superoxide-dependent and ascorbate-dependent formation of hydroxyl radicals in the presence of copper salts: a physiologically significant reaction? 631 Nov 5

We have previously reported the purification of polypeptides from soybean which are potent inhibitors of superoxide production by human neutrophils. We now report that neither oxygen uptake nor hydrogen peroxide production by stimulated neutrophils is affected by these inhibitors. Furthermore, the E-1 and E-3 polypeptides inhibit ferricytochrome c reduction by a xanthine oxidase superoxide generation system. The inhibitory activity of E-3 in the model system is blocked by 1 mM KCN while E-1 is only slightly cyanide sensitive. Atomic absorption analysis of E-1 and E-3 polypeptides reveal copper in the latter and manganese in the former. Thus, E-3 is a copper-containing superoxide dismutase while E-1 appears to be a manganese-containing superoxide dismutase.
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PMID:Pseudo-inhibitors of neutrophil superoxide production: evidence that soybean-derived polypeptides are superoxide dismutases. 631 48

NAD(P)H oxidation is frequently measured to assay the activity of the neutrophil O-2-generating oxidase. It was found that 10(-4) M ethylene glycol bis (beta-aminoethyl ether)-N-N'-tetraacetic acid (EGTA) increased NAD(P)H oxidation by the 27,000 g granule fraction of resting and stimulated human neutrophils without altering net O-2 production. The commonly used chelating agents EDTA and diethylene triamine pentaacetic acid had similar effects. The addition of superoxide dismutase eliminated the effect of the chelating agents and thus demonstrated that the stimulated reaction was dependent upon O-2. KCN and bathophenanthroline disulfonate, an iron-chelating agent, prevented O-2-dependent NADPH oxidation by neutrophil granule fractions in the presence of EGTA. In contrast, bathocuproine disulfonate, a copper-chelating agent, mimicked the EGTA effect. The effects of both bathophenanthroline disulfonate and bathocuproine disulfonate were completely abolished when the agents were saturated with iron and copper, respectively. All the chelating agents studied, except bathophenonthroline disulfonate, also promoted O-2-dependent NADPH oxidation in a system wherein O-2 was generated by xanthine oxidase. Thus, commonly used chelating agents, by interacting with available iron and copper, may alter the apparent stoichiometry of the neutrophil O-2-generating oxidase and artifactually increase NADPH oxidation in other systems where O-2 is present.
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PMID:Effect of chelating agents and superoxide on human neutrophil NAD(P)H oxidation. 632 25

Very little is known of the metabolism of copper on a molecular level. For example, there is no evidence of an oxidative breakdown of Cu(I)-thionein leading to Cu(II). Thus it was of interest to use L- and D-amino-acid oxidases, amino oxidase and galactose oxidase to control the oxidation of Cu(I)-thionein by enzymically generated H2O2. In the presence of these enzymes Cu(II) was generated in each case. In a more detailed study the Cu(I)-thiolate chromophores of Cu-thionein were oxidized in the presence of xanthine oxidase as deduced from spectrometrical measurements using EPR and circular dichroism. Unlike Cu2Zn2-superoxide dismutase catalase inhibited the oxidative cleavage, suggesting peroxide as the actual oxidizing agent. Possibly there is an enzymic oxidative pathway for the generation of biologically important Cu(II).
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PMID:Oxidation of Cu(I)-thionein by enzymically generated H2O2. 654 80

The superoxide dismutase (EC 1.15.1.1) activities of new series of macrocyclic complexes with copper(II) have been measured. Chemical modifications in macrocyclic ring size, donor atom, donor atom number, substituents on the macrocyclic skeletons, and length of bridges linking two macrocycles are shown to have profound effects on the superoxide dismutase activities of the metal complexes. The quantitative measurement by the standard xanthine-xanthine oxidase assay, which depends on the conversion of nitroblue tetrazolium to formazan, has been corroborated by a direct assay method using an oxygen electrode.
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PMID:Further studies on superoxide dismutase activities of macrocyclic polyamine complexes of copper(II). 668 11

The trace elements iron, copper, and zinc and the minerals calcium and magnesium have been found associated to human milk fat. After solubilization of milk fat globule membranes with detergent, the major part of these elements within the fat fraction were found in the more hydrophilic outer fat globule membrane: Fe 61%, Cu 73%, Zn 64%, Ca 67%, and Mg 71%. Most of the remainder was found in the more hydrophobic inner membrane, while only small amounts of the elements were associated with the core triglyceride fraction. Gel filtration chromatography on Sepharose CL-6B indicates the major iron- and zinc-binding proteins in the outer membrane are xanthine oxidase and alkaline phosphatase.
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PMID:Iron, copper, zinc, calcium, and magnesium in human milk fat. 669 23

Amounts of Copper/zinc containing superoxide dismutase have been found in human seminal plasma. Superoxide dismutase inhibits the lipid peroxidation in the xanthine oxidase system. In seminal plasma of spermatozoa with a good motility the superoxide dismutase activity is higher than in those with a low motility.
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PMID:Superoxide dismutase in human semen. 683 45

A procedure has been developed to distinguish between the two forms of eukaryotic superoxide dismutases using a common activity assay. Treatment of cellular fractions with 2% sodium dodecyl sulfate at 37 degrees C for 30 min selectively inactivates the mitochondrial, manganese-containing variant without affecting the cytosolic copper, zinc-superoxide dismutase. After removing excess sodium dodecyl sulfate by precipitation with potassium chloride, the supernate is assayed using the xanthine oxidase-cytochrome c method.
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PMID:A method for distinguishing Cu,Zn- and Mn-containing superoxide dismutases. 684 3

Interaction between 6-mercaptopurine, Cu2+ and the enzyme xanthine oxidase (EC 1.2.3.2.) was examined. Whereas Cu2+ was found to inhibit the enzyme, 6-mercaptopurine could protect as well as reverse the enzyme inhibition produced by the metal ion. The formation of a complex between 6-mercaptopurine and Cu2+ seems to be responsible for the observed effect. Job's [(1928) Ann. Chem. 9, 113] method has shown the composition of the complex to be 1:1. The apparent stability constant (log K value), as determined by Subhrama Rao & Raghav Rao's [(1955) J. Sci. Chem. Ind. Res. 143, 278], method is found to be 6.74. It is suggested that the formation of a stable complex between 6-mercaptopurine molecules and Cu2+ may be an additional mechanism of action of 6-mercaptopurine, particularly with reference to its anti-inflammatory properties.
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PMID:Studies on the mechanism of action of 6-mercaptopurine. Interaction with copper and xanthine oxidase. 689 65

Copper(II) and nickel(II) complexes of macrocyclic polyamine derivatives possessing partial oligopeptide-like structures are found to suppress the xanthine-xanthine oxidase-mediated reduction of nitroblue tetrazolium and also to suppress formazan formation by potassium superoxide. The activity in the superoxide dismutase assay is dependent on ring size, type and number of donor atoms, metal ion, and substituents on the macrocycles. Some of those are more active than the known O2- scavengers such as copper(II)-salicylate and copper(II)-amino acid (or peptide) complexes. Nickel (II)-naphthylmethyl-dioxo-[16]ane N5, 13, 1:1 complex (NiH-2L) is the most active among the 30 chelates examined.
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PMID:Superoxide dismutase activity of macrocyclic polyamine complexes. 689 4


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