Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P47989 (xanthine oxidase)
 8,633 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Superoxide dismutase (SOD) activity was measured in the maternal and cord blood by the modified method of Beauchamp and Fridovich, using a carbonate-buffered (pH 10.2) xanthine-xanthine oxidase system. No great differences between maternal and cord blood in erythrocyte SOD levels were observed, with the exception of whole blood; namely, washed RBC showed a SOD activity of a fairly high level, which was comparable to the activities of crude SOD, but showed no difference between them. In contrast, the SOD activity in the maternal whole blood was significantly lower than that in the cord blood. In measuring SOD activity, the serum factor has a great effect, and serum contains a substance that inhibits NBT reduction. Only one band of SOD has been detected which shows identical Rf values both in maternal and cord blood by polyacrylamide-gel electrophoresis.
 ...
PMID:Superoxide dismutase activity in the maternal and cord blood. 48 7

A polarographic method to assess the scavenging capacity of a molecule for O2-. is proposed. This method is based on the fact that O2-. is not detected by the Clark electrode and that a scavenger competes with spontaneous dismutation of O2-. So, the reduction of O2 into O2-. and the decomposition of H2O2 by catalase, releasing O2, show a biphasic kinetic. Various kinetic parameters can be used to calculate the nmol of O2-. scavenged and also supply data on the reaction mechanisms (oxidation or reduction of O2-.) involved in scavenging. This method presents several other advantages: scavenging capacity can be assayed without added indicators which themselves behave as scavengers (as demonstrated for NBT), the presence of scavengers which interfere with the O2-. generating system (xanthine-xanthine oxidase) does not invalidate the measurements made.
 ...
PMID:Superoxide anion scavenging capacity measured by a polarographic method. Comparison with a colourimetric method. 133 24

Ultrathin isoelectric focusing was employed for analyzing xanthine oxidase and enzymes with NADH-dependent dehydrogenase activity in homogenates of rat kidney. After isoelectric focusing the enzymes were stained with specific assays where NBT is reduced upon incubation of the gel with xanthine (oxidase stain) and NADH (dehydrogenase stain) as substrates. A good separation of renal enzymes with dehydrogenase activities was obtained by using gels containing 2 M urea and by applying the sample at the anode. In these conditions 4 main isoforms with pI 6.4, 6.35, 6.5 and 6.6 were observed with the dehydrogenase stain but we were unable to demonstrate renal xanthine oxidase (XO) which seemed to be due to precipitation at the application point.
 ...
PMID:Analysis by isoelectric focusing of xanthine oxidase and NADH dependent enzymes in rat kidney. 209 5

Superoxide dismutase (SOD) activity in cow snout epidermis was determined by the method of electron spin resonance (ESR) using the 5, 5 dimethyl-1-pyrroline-N-oxide (DMPO) spin trapping agent. The procedure was found to be a reliable measurement as compared with the ordinary method using xanthine oxidase NBT. SOD activity was distributed through the whole epidermis. This activity was higher in the lower layer than in the upper and middle layers.
 ...
PMID:Distribution of superoxide dismutase activity in the epidermis: measurement with electron spin resonance spin trapping. 215 33

Myeloperoxidase catalyses the conversion of H2O2 and Cl- to hypochlorous acid (HOCl). It also reacts with O2- to form the oxy adduct (compound III). To determine how O2- affects the formation of HOCl, chlorination of monochlorodimedon by myeloperoxidase was investigated using xanthine oxidase and hypoxanthine as a source of O2- and H2O2. Myeloperoxidase was mostly converted to compound III, and H2O2 was essential for chlorination. At pH 5.4, superoxide dismutase (SOD) enhanced chlorination and prevented formation of compound III. However, at pH 7.8, SOD inhibited chlorination and promoted formation of the ferrous peroxide adduct (compound II) instead of compound III. We present spectral evidence for a direct reaction between compound III and H2O2 to form compound II, and for the reduction of compound II by O2- to regenerate native myeloperoxidase. These reactions enable compound III and compound II to participate in the chlorination reaction. Myeloperoxidase catalytically inhibited O2- -dependent reduction of Nitro Blue Tetrazolium. This inhibition is explained by myeloperoxidase undergoing a cycle of reactions with O2-, H2O2 and O2-, with compounds III and II as intermediates, i.e., by myeloperoxidase acting as a combined SOD/catalase enzyme. By preventing the accumulation of inactive compound II, O2- enhances the activity of myeloperoxidase. We propose that, under physiological conditions, this optimizes the production of HOCl and may potentiate oxidant damage by stimulated neutrophils.
 ...
PMID:Superoxide modulates the activity of myeloperoxidase and optimizes the production of hypochlorous acid. 284 72

A new method for the determination of xanthine oxidase activity, based on the oxidation of 2,2'-azino-di(3-ethylbenzthiazoline-6-sulphonate) (ABTS) by use of uricase and peroxidase, is described. The absorbance increase of the oxidized form of ABTS, measured after 10 min at 410 nm is proportional to xanthine oxidase activity. The method is sensitive, precise (CV below 8.3%), and linear up to 20 U/l. The analytical recovery of the ABTS-method was quantitative. Comparison with the UV and colorimetric NBT-method gave good correlation (r greater than or equal to 0.984). Reference values for serum xanthine oxidase activities determined with the new ABTS-method on 83 healthy persons are 0 to 1.20 U/l.
 ...
PMID:Spectrophotometric assay of xanthine oxidase with 2,2'-azino-di(3-ethylbenzthiazoline-6-sulphonate) (ABTS) as chromogen. 380 44

The possible role of superoxide anion in 2-oxoglutarate-coupled dioxygenase reactions has been investigated. gamma-Butyrobetaine hydroxylase (EC 1.14.11.1) was inhibited by human erythrocyte superoxide dismutase (EC 1.15.1.1), probably due to release of Cu(2+) or Zn(2+), as the inhibition was more pronounced after heat-inactivation of the dismutase and as Cu(2+) was a potent inhibitor. Bovine superoxide dismutase and the Mn(2+)-containing superoxide dismutase from Escherichia coli were not inhibitory. Superoxide anion generated from xanthine/xanthine oxidase was not stimulatory and could not replace ascorbate. Thymine 7-hydroxylase (EC 1.14.11.6) and thymidine 2'-hydroxylase (EC 1.14.11.3) were not inhibited by erythrocyte superoxide dismutase or stimulated by superoxide anion. gamma-Butyrobetaine hydroxylase was inhibited by a number of low-molecular-weight compounds, such as tetranitromethane, Nitro Blue Tetrazolium, adrenaline and Tiron, which may act as scavengers of superoxide anion. Involvement of this radical in other oxygenase reactions has been inferred from the findings that they were inhibitory for the respective enzymes. Several of these compounds also inhibited gamma-butyrobetaine hydroxylase. It could be concluded from these experiments, however, that mechanisms other than disposal of superoxide anion might equally well be operative, such as hydrophobic interaction with the enzyme protein and interaction with compounds required for full enzymic activity, e.g. iron and ascorbate. The results appear to rule out a requirement for superoxide anion generated in free solution, and have not yielded evidence for participation of enzyme-bound superoxide anion in 2-oxoglutarate-dependent hydroxylations.
 ...
PMID:Does superoxide anion participate in 2-oxoglutarate-dependent hydroxylation? 629 7

Metallothionein inhibited in a concentration-dependent fashion the reduction of nitroblue tetrazolium [NBT] mediated by xanthine oxidase and by NADH-phenazine methosulfate. This catalytic activity of metallothionein for dismutation of O2- is dependent on the copper content in metallothionein.
 ...
PMID:Inhibition of nitroblue tetrazolium reduction by metallothionein. 689 6

The antioxidant properties of silibin complexes, the water-soluble form silibin dihemisuccinate (SDH), and the lipid-soluble form, silibin phosphatidylcholine complex known as IdB 1016, were evaluated by studying their abilities to react with the superoxide radical anion (O2-.), and the hydroxyl radical (OH.). In addition, their effect on pulmonary and hepatic microsomal lipid peroxidation had been investigated. Superoxide radicals were generated by the PMS-NADH system and measured by their ability to reduce NBT. IC50 concentrations for the inhibition of the NBT reduction by SDH and IdB 1016 were found to be 25 microM and 316 microM respectively. Both silibin complexes had an inhibitory effect on xanthine oxidase activity. SDH reacted rapidly with OH radicals at approximately diffusion controlled rate and the rate constant was found to be (K = 8.2 x 10(9) M-1 s-1); it appeared to chelate Fe2+ in solution. In hepatic microsomes, when lipid peroxidation was induced by Fe2+, SDH inhibited by 39.5 per cent and IdB 1016 by 19.5 per cent, whereas when lipid peroxidation was induced by CuOOH, IdB 1016 exerted a better protective effect than SDH (29.4 per cent and 19.4 per cent inhibition, respectively). In both microsomal systems lipid peroxidation proceeded through a thiol depletion mechanism which could be restored in the presence of silibin complexes. Low levels of lipid peroxidation in pulmonary microsomes point out the differences between in-vitro lipid peroxidation occurring in microsomes of different tissues. The results support the free radical scavenger and antioxidative properties of silibin when it is complexed with a suitable molecule to increase its bioavailability.
 ...
PMID:Free radical scavenging and antioxidative properties of 'silibin' complexes on microsomal lipid peroxidation. 907 34

The tetrazolium dyes MTS and XTT were reduced to their soluble formazans by superoxide radical anions (O2-) produced by the oxidation of xanthine by xanthine oxidase under standard conditions. These reactions were compared to the well-known reductions of NBT and cytochrome c by the xanthine/xanthine oxidase system. Reduction of the dyes was completely inhibited by superoxide dismutase (SOD). Rate constants for the reaction of MTS and XTT with O2- were estimated at 1.3 +/- .1 x 10(5) M-1S-1 and 8.6 x 10(4) M-1S-1 respectively. The stable MTS and XTT formazans have high extinction coefficients in the visible range which enable sensitive detection and quantification of superoxide radicals, avoiding some of the problems inherent in assays based on production of the insoluble NBT formazan. MTS and XTT have considerable potential both for the quantitative assay of radical production in living tissues and for the assay of superoxide dismutase activity in tissue extracts. Implications for the interpretation of cell culture growth assays which employ these dyes are discussed.
 ...
PMID:The tetrazolium dyes MTS and XTT provide new quantitative assays for superoxide and superoxide dismutase. 935 Apr 32


1 2 3 4 Next >>