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Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The study of the participation of metals in evolution of oxidation-reduction processes is subdivided into two periods. During the first of them, from 1897 to 1937, the significance of manganese, iron, titanium, molybdenum, vanadium and copper in most important processes of metabolism was discovered. The second period, from 1937 to 1977, was devoted to the study of the role of metals in individual representatives of oxidoreductases and their evolution during transition of organisms from anaerobiosis to aerobiosis. In this evolution of special importance were bimetallic enzymes, such as nitrogenase, some nitrate reductases and hydrogenases, carbon dioxide reductase, xanthine oxidase, cytochrome oxidase. Owing to their ability to accomplish conjugated oxidation-reduction reactions, these oxidoreductases were transitional to still more complicated polymetallic systems with whose participation the electron transfer chains in subcellular structures were formed.
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PMID:[Participation of polyvalent metals in the evolution of oxidoreductases]. 91 1

Vanadium compounds are known to stimulate the oxidation of NAD(P)H, but the mechanism remains unclear. This reaction was studied spectrophotometrically and by electron spin resonance spectroscopy (ESR) using vanadium in the reduced state (+4, vanadyl) and the oxidized state (+5, vanadate). In 25 mM sodium phosphate buffer at pH 7.4, vanadyl was slightly more effective in stimulating NADH oxidation than was vanadate. Addition of a superoxide generating system, xanthine/xanthine oxidase, resulted in a marked increase in NADH oxidation by vanadyl, and to a lesser extent, by vanadate. Decreasing the pH with superoxide present increased NADH oxidation for both vanadate and vanadyl. Addition of hydrogen peroxide to the reaction mixture did not change the NADH oxidation by vanadate, regardless of concentration or pH. With vanadyl however, addition of hydrogen peroxide greatly enhanced NADH oxidation which further increased with lower pH. Use of the spin trap DMPO in reaction mixtures containing vanadyl and hydrogen peroxide or a superoxide generating system resulted in the detection by ESR of hydroxyl. In each case, the hydroxyl radical signal intensity increased with vanadium concentration. Catalase was able to inhibit the formation of the DMPO--OH adduct formed by vanadate plus superoxide. These results show that the ability of vanadium to act in a Fenton-type reaction is an important process in the vanadium-stimulated oxidation of NADH.
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PMID:Importance of hydroxyl radical in the vanadium-stimulated oxidation of NADH. 253 40

The inhibition of the activity of xanthine oxidase by vanadate was strikingly similar to vanadate inhibition of another molybdoprotein nitrate reductase. Although the main catalytic activity of both enzymes was inhibited, the partial NADH oxidase activity associated with these enzymes was stimulated several fold. It appears that the metal ion binds at multiple site in both enzymes. In the absence of any enzymes a combination of vanadium (V) and molybdenum (V) in air was found to oxide NADH rapidly.
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PMID:Effects of vanadate on the molybdoproteins xanthine oxidase and nitrate reductase: kinetic evidence for multiple site interaction. 689 79

When Escherichia coli was incubated with xanthine oxidase and acetaldehyde, the killing of E. coli was accelerated by iron-EDTA but inhibited by hematin or hemoglobin. On the other hand, when E. coli was incubated with human neutrophils in the presence of phorbol myristate acetate (PMA), all of these iron species at concentrations of a few micromolar accelerated the inactivation of neutrophils and in so doing protected the E. coli from being killed by the neutrophils. The inactivation of the neutrophils was accompanied by an increase in lipid peroxidation and by a decrease in viability measured with trypan blue. This inactivation was inhibited by scavengers such as deoxyribose, mannitol, or thiourea. Desferrioxamine B and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) both inhibited the inactivation mediated by iron-EDTA, but had no effect on the hematin- or hemoglobin-mediated inactivation. Vanadium (vanadyl ion), an effective Fenton reagent, behaved in the same way as iron-EDTA relative to the effects of DMPO on neutrophil inactivation. These results led us to conclude that neutrophils were inactivated during PMA stimulation by OH radicals in the presence of iron-EDTA and by some other oxidizing species when hematin or Hb is present. Ascorbate enhanced the inactivation of neutrophils mediated by these iron species. Catalase was very effective in inhibiting neutrophil inactivation. Superoxide dismutase was not as effective but the combination with catalase was most effective.
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PMID:The effect of hemoglobin, hematin, and iron on neutrophil inactivation in superoxide generating systems. 813 43

This study was undertaken to investigate the effects of vanadium in the +2, +3, +4, and +5 valence states on superoxide generation, myeloperoxidase (MPO) activity, and hydroxyl radical formation by activated human neutrophils in vitro, using lucigenin-enhanced chemiluminescence (LECL), autoiodination, and electron spin resonance with 5,5-dimethyl-l-pyrroline N-oxide as the spin trap, respectively. At concentrations of up to 25 microM, vanadium, in the four different valence states used, did not affect the LECL responses of neutrophils activated with either the chemoattractant, N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 microM), or the phorbol ester, phorbol 12-myristate 12-acetate (25 ng/ml). However, exposure to vanadium in the +2, +3, and +4, but not the +5, valence states was accompanied by significant augmentation of hydroxyl radical formation by activated neutrophils and attenuation of MPO-mediated iodination. With respect to hydroxyl radical formation, similar effects were observed using cell-free systems containing either hydrogen peroxide (100 microM) or xanthine/xanthine oxidase together with vanadium (+2, +3, +4), while the activity of purified MPO was inhibited by the metal in these valence states. These results demonstrate that vanadium in the +2, +3, and +4 valence states interacts prooxidatively with human neutrophils, competing effectively with MPO for hydrogen peroxide to promote formation of the highly toxic hydroxyl radical.
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PMID:Vanadium promotes hydroxyl radical formation by activated human neutrophils. 1633 88

Coherent radiation from undulator beamlines has been used to directly measure the real and imaginary parts of the index of refraction of several materials at both extreme-ultraviolet and soft-x-ray wavelengths. Using the XOR interferometer, we measure the refractive indices of silicon and ruthenium, essential materials for extreme-ultraviolet lithography. Both materials are tested at wavelength (13.4 nm) and across silicon's L2 (99.8 eV) and L3 (99.2 eV) absorption edges. We further extend this direct phase measurement method into the soft-x-ray region, where measurements of chromium and vanadium are performed around their L3 absorption edges at 574.1 and 512.1 eV, respectively. These are the first direct measurements, to our knowledge, of the real part of the index of refraction made in the soft-x-ray region.
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PMID:Direct index of refraction measurements at extreme-ultraviolet and soft-x-ray wavelengths. 1657 88

The inhalation of vanadium pentoxide (V(2)O(5)) results in bronchitis and airway fibrosis. The lung fibrotic response to V(2)O(5) partially resolves where fibroblasts first proliferate and deposit collagen, but then undergo growth arrest and apoptosis. STAT-1 mediates fibroblast growth arrest and apoptosis. We previously reported that STAT-1 is a protective factor and mice lacking STAT-1 are more susceptible to lung fibrosis. We also reported that V(2)O(5)-induced STAT-1 phosphorylation in lung fibroblasts requires H(2)O(2) and de novo protein synthesis. In this study, we identified IFN-beta as the protein that mediates STAT-1 activation by V(2)O(5) in normal human lung fibroblasts and identified NADPH and xanthine oxidase systems as sources of H(2)O(2) that drive IFN-beta gene expression. STAT-1 phosphorylation was decreased with neutralizing Abs to IFN-beta as well as an inhibitor of JAK. V(2)O(5) also increased transcription of an IFN-inducible and STAT-1-dependent chemokine, CXCL10. Inhibition of H(2)O(2)-generating enzyme systems NADPH oxidase by apocynin and xanthine oxidase by allopurinol individually reduced STAT-1 phosphorylation. Apocynin and allopurinol also decreased V(2)O(5)-induced IFN-beta mRNA levels and CXCL10 expression. IFN-alpha transcription was inhibited only by allopurinol. Taken together, these data indicate that fibroblasts play a role in the innate immune response to vanadium-induced oxidative stress by synthesizing IFN-beta and activating STAT-1 to cause growth arrest and increase levels of CXCL10, a potent antifibrotic factor. This mechanism is postulated to counterbalance profibrogenic mechanisms that follow V(2)O(5) injury.
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PMID:STAT-1 signaling in human lung fibroblasts is induced by vanadium pentoxide through an IFN-beta autocrine loop. 1832 32

The inhibitory effect of selected metal ions [Ag(I), Hg(II), Cu(II), Cr(VI), V(V), Au(III), T1(I) and Zn(II)], on the xanthine oxidase (XOD) catalysis of xanthine oxidation, has been investigated with reference to the XOD catalysis of oxidation of NADH. Hg(II), Ag(I), Zn(II) and Au(III) act as inhibitors, T1(I) has no effect and Cu(II), Cr(VI) and V(V) act as activators. The formation of O(2)(-) during XOD catalysis of oxidation of either xanthine or NADH has also been studied. All the metal ions considered act as inhibitors with respect to O(2)(-) production when the reducing substrate is xanthine, but only a few of them when the substrate is NADH, the others showing no effect whatsoever whether or not they activate NADH oxidation in the course of the same reaction. Vanadium (V) has an anomalous effect: it inhibits xanthine oxidation but considerably increases NADH oxidation, and thus appears to modify the catalytic properties of the enzyme. This behaviour appears promising as the basis for a kinetic method for determination of V(V).
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PMID:Influence of some metal ions on oxidation of nadh and on formation of the superoxide anion radical (O(2)(-)), during enzymatic catalysis by E.C. 1.2.3.2 xanthine oxidase. 1896 60

An enzymatic kinetic method for the determination of V(V) is described, based on the activation of xanthine oxidase-catalysed NADH oxidation, in the presence of xanthine, dithiothreitol and Ag(+) ions. Under these conditions the activating power of V(V) was found to be enhanced. The linear relationship between relative enzyme activity and V(V) concentration allows the enzymatic determination of vanadium in the concentration range 20-500 ng ml , the maximum relative error being +/- 3%, and relative standard deviation less than +/- 2.2%. Possible interferences have been studied.
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PMID:Use of enzymatic catalysis with E.C. 1.2.3.2 xanthine oxidase for the kinetic determination of V(V) at low concentrations. 1896 35

The present study explores the synthesis and inhibitory potential of vanadium(V) complexes of hydrazides (1c-12c) against oxidative enzymes including xanthine oxidase and lipoxygenase (LOX). In addition, non-enzymatic radical scavenging activities of these complexes were also determined. On the basis of spectral, elemental and physical data, synthesized vanadium(V) complexes are tentatively assigned to have an octahedral geometry with two hydrazide ligands and two oxo groups forming a negatively charged sphere complex with ammonium as counter ion. This is further verified by the conductivity studies of the complexes. Results show that hydrazide ligands (1-12) and their respective vanadium(V) complexes (1c-12c) posses scavenging and inhibition potential against DPPH and LOX, respectively. However, contrary to that uncoordinated ligands showed no activity against nitric oxide, superoxide and xanthine oxidase whereas their complexes showed varying degree of activity. These studies indicate that geometry of complex, nature and position of substituent groups play a vital role in scavenging and inhibition potential of these compounds.
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PMID:Vanadium(V) complexes with hydrazides and their spectroscopic and biological properties. 2899 11


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