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

Coformycin, which is an inhibitor of adenosine deaminase, significantly inhibited in vitro blastogenic responses of human lymphocytes to both phytohaemagglutinin (PHA) and pokeweed mitogen (PWM), whereas blastogenic responses to bacterial lipopolysaccharide (LPS) were rather enhanced by the addition of coformycin. Blastogenic responses of lymphocytes to PHA and PWM were markedly suppressed by the addition of adenosine, which is a substrate of adenosine deaminase. Allopurinol, which is an inhibitor of xanthine oxidase, inhibited blastogenic responses of human lymphocytes to PHA, PWM, and bacterial LPS. Inosine (a substrate of purine nucleoside phosphorylase) and hypoxanthine (a substrate of xanthine oxidase) showed no or only a small effect on blastogenic responses of human lymphocytes. These results suggest that adenosine deaminase activity is associated with the T-cell response but not with the B-cell response and that the impaired T-cell response in adenosine deaminase deficiency is the result of intracellular retention of adenosine in T cells. The results also suggest that purine nucleoside phosphorylase or xanthine oxidase activity is associated with both T- and B-cell responses.
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PMID:Purine metabolic enzymes in lymphocytes. IV. Effects of enzyme inhibitors and enzyme substrates on the blastogenic responses of human lymphocytes. 392 75

A direct colorimetric assay for inorganic phosphate in serum is described. The system is based on utilization of the enzymes, purine-nucleoside phosphorylase and xanthine oxidase, to generate superoxide ions. The superoxide is measured in the presence of an electron mediator compound with 3-(4',5'-dimethyl-2-thiazolyl)-2,4-diphenyl-2H-tetrazolium bromide as the chromogen. The high absorbance of this chromogen between 550 and 660 nm affords useful results with a sample/reagent volume ratio as low as 1:100. A single working reagent is used, and the reaction is complete in 15 min at room temperature. The standard curve is linear for inorganic phosphate concentrations as high as 4.9 mmol/liter. Analytical recovery of phosphate in human sera averages 100%. Within-run precision study gives CV less than or equal to 1.0%. The results of this method compare closely (r greater than 0.99) with those obtained by the semidine method (recommended standard). The method lends itself to automation.
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PMID:Phosphate determination by enzymatic colorimetric assay. 393 4

Because of the importance of adenosine deaminase (ADA) in brain function, a histochemical method for visualizing the enzyme in various areas of the human neuraxis was devised, using an MTT [3-(4,5-dimethyl-thiazolyl-2)-2,5-diphenyltetrazolium bromide] method and glutaraldehyde fixation. Controls consisted of preincubation without the substrate, incubation with omission successively of the substrate, MTT tetrazolium, purine nucleoside phosphorylase (PNP), xanthine oxidase (XO), NaCl, boiling for 20 min prior to fixation and incubation, and of incubation of sections with two powerful inhibitors of the enzyme, i.e., 2'-deoxycoformycin and EHNA [erythro-9-(2-hydroxy-3-nonyl)adenine.HCl]. The positive reaction consisted of the deposition of brownish-purple granules, as well as a diffuse nongranular reaction in the cytoplasm of neurons and glial cells, and in the interstitial spaces. Sections from 15 different areas in four brains were examined by this method. This is the first time that adenosine deaminase has been demonstrated histochemically in the nervous system of humans or of any other species.
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PMID:Histochemical demonstration of adenosine deaminase in the human neuraxis. Preliminary observations. 404 5

Plasmodium falciparum trophozoites were isolated by mechanical rupture of infected human erythrocytes followed by a series of differential centrifugation steps. After lysis with sonication, the 100 000 x g supernatant of parasites and uninfected host cells was used to determine the specific activities of a number of enzymes involved in purine and pyrimidine metabolism. P. falciparum possessed the purine salvage enzymes: adenosine deaminase, purine nucleoside phosphorylase, hypoxanthine-guanine phosphoribosyltransferase (PRTase), xanthine PRTase, adenine PRTase, adenosine kinase. The last two enzymes, however, were present at much lower activity levels. Hypoxanthine was converted (presumably via IMP) into adenine and guanine nucleotides only in the presence both of supernatant and membrane fractions of P. falciparum. Two enzymes involved in the de novo synthesis of pyrimidines, orotic acid PRTase, and orotidine 5'-phosphate decarboxylase, were present in parasite extracts as were the enzymes for pyrimidine nucleotide phosphorylation: UMP-CMP kinase, dTMP kinase, nucleoside diphosphate kinase. Xanthine oxidase, CTP synthetase, cytidine deaminase and several kinases for the salvage of pyrimidine nucleosides were not detected in the parasites. Both phosphoribosyl pyrophosphate synthetase and uracil PRTase were present but at low activity levels. Human erythrocytes displayed similar but not identical enzyme patterns. Enzyme specific activities, however, were generally much lower than those of the corresponding parasite enzymes.
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PMID:Enzymes of purine and pyrimidine metabolism from the human malaria parasite, Plasmodium falciparum. 628 90

The purine metabolism of four cases with marked hypouricemia (serum uric acid concentration of less than 0.018 mmol/l) from three Japanese families was investigated. Erythrocyte adenosine deaminase (EC 3.5.4.4) and purine-nucleoside phosphorylase (EC 2.4.2.1) activities of the patients were within the normal ranges. Urinary hypoxanthine and xanthine concentrations were 0.096-0.397 mmol/l and 0.743-1.717 mmol/l, respectively. Xanthine oxidase (EC 1.2.3.2) activities in the jejunal mucosa of the two normal controls were 0.257 and 0.283 units/g protein, while those of three of the patients were extremely low and could not be determined. The findings of these biochemical features may indicate that the four patients have hereditary xanthinuria. In order to study the purine metabolism in the hypouricemic condition of this disorder, a single oral dose of allopurinol (4-hydroxypyrazolo[3,4-d]pyrimidine) was administered in one case. The excretion pattern of allopurinol and oxypurinol (4,6-dihydroxypyrazolo[3,4-d]pyrimidine) in the urine of the patient was similar to that of a normal control male. These data suggest that some residual enzyme activity may be functioning in vivo, although the presence of xanthine oxidase could not be detected.
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PMID:Biochemical studies on the purine metabolism of four cases with hereditary xanthinuria. 642 23

A spectrophotometric method especially suitable for biological materials is described for the determination of purine nucleoside phosphorylase activity. In combination with the enzymes xanthine oxidase, catalase and aldehyde dehydrogenase, and in the presence of ethanol and NAD(P), the purines formed by phosphorylysis of purine nucleosides are oxidized and the absorption of the NAD(P)H formed is taken for the calculation of nucleoside phosphorylase activity.
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PMID:A new spectrophotometric assay for enzymes of purine metabolism. III. Determination of purine nucleoside phosphorylases. 676 4

In cancer cells, a marked imbalance in the enzymic pattern of purine metabolism is linked with transformation and/or progression. In chemically-induced, transplantable hepatomas in rat, the specific activities of the anabolic enzymes, IMP dehydrogenase, GMP synthetase, adenylosuccinate synthetase, adenylosuccinase, AMP deaminase and amidophosphoribosyltransferase, increased to 13.5-, 3.7-, 3.1-, 1.8-, 5.5- and 2.8-fold, respectively, of those in normal liver. Activities of the catabolic enzymes, inosine phosphorylase, xanthine oxidase and uricase, decreased to 19, 10 and 4%, respectively. This enzymic imbalance was specific to hepatic neoplasia, since no similar pattern was observed in differentiating or regenerating liver. Most enzymic alterations were present also in chemically- and virus-induced animal tumors, in human kidney, liver and colon carcinomas, and in human colon carcinoma xenografts. The molecular correlation concept applies to purine biochemistry and an important segment of neoplastic gene expression was identified in the behavior of key purine-metabolizing enzymes.
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PMID:Enzymes of purine metabolism in cancer. 686 38

A high-performance liquid chromatographic method was developed for the determination of plasma purine nucleoside phosphorylase activity. In this method, the reaction mixture consisted of 15 microliters of plasma and 285 microliters of 50 mM phosphate buffer (pH 7.4) containing 3.8 mM inosine and 0.15 mM 2-(3-cyano-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid (strong xanthine oxidase inhibitor). After the reaction, the hypoxanthine produced was monitored to express plasma purine nucleoside phosphorylase activity. By this method, the activity of purine nucleoside phosphorylase was easily determined even with a small-volume plasma sample and despite its low activity in plasma. In addition, plasma purine nucleoside phosphorylase activity can be accurately determined even if the plasma is turbid. As a result, we were able to measure plasma purine nucleoside phosphorylase activity in patients with gout or asthma and healthy subjects, whereby it was demonstrated that plasma purine nucleoside phosphorylase activity was higher in patients with asthma than in either healthy subjects or patients with gout.
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PMID:Determination of plasma purine nucleoside phosphorylase activity by high-performance liquid chromatography. 766 72

The activities of five enzymes involved in purine salvage and catabolism--hypoxanthine phosphoribosyl transferase (HPRT), adenine phosphoribosyl transferase (APRT), adenosine deaminase (ADA), purine nucleoside phosphorylase (PNP) and guanase--were measured in mouse embryo extracts, from the one-cell to the blastocyst stage. Xanthine oxidase activity was not detected. The analyses were performed using high performance liquid chromatography and the enzymes showed different patterns of activity during development. Activities of HPRT, APRT and PNP were low before morula formation, and then increased until the blastocyst stage. ADA and guanase showed high activities after fertilization; guanase activity decreased sharply after the two-cell stage and ADA activity decreased sharply after the morula stage. Blastocyst formation was accompanied by a further decline in activity of both enzymes. The methods used may be suitable for measuring these enzymes in single human embryos, or in biopsies derived from them.
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PMID:Enzymes of purine salvage and catabolism in the mouse preimplantation embryo measured by high performance liquid chromatography. 806 75

This study was undertaken to examine the metabolism of hypoxanthine by mouse oocyte-cumulus cell complexes. Complexes were isolated from immature mice 48 h after priming with 5 IU eCG and culture for 3 h in medium containing 14C-hypoxanthine in the absence or presence of one of three metabolic inhibitors: alanosine, mycophenolic acid, or 6-mercaptopurine. Tissue extracts from complexes were analyzed by HPLC using either a C18 reversed-phase column (for separation of purine bases and nucleosides) or an ion exchange column (for separation of nucleotides). Most of the hypoxanthine taken up by complexes was salvaged to inosine monophosphate (IMP) and then converted to nucleotides. Metabolism favored the synthesis of adenyl nucleotides over guanyl nucleotides. No evidence of metabolism to uric acid via xanthine oxidase was encountered, and metabolism to inosine via purine nucleoside phosphorylase was negligible. A similar pattern of hypoxanthine metabolism was observed in extracts of oocytes that had been denuded after the culture period. Addition of alanosine to the culture medium significantly reduced the synthesis of adenyl nucleotides in complexes and partially shunted metabolism in the direction of guanyl nucleotides. However, neither alanosine nor another inhibitor of adenylosuccinate synthetase, hadacidin, significantly influenced the meiotic arrest maintained by hypoxanthine. Mycophenolic acid eliminated conversion of IMP to guanyl nucleotides but did not appreciably affect metabolism to other nucleotides. 6-Mercaptopurine produced an increase in the hypoxanthine-containing peaks, which was consistent with suppression of purine salvage. These results demonstrate that hypoxanthine is readily salvaged by the murine oocyte-cumulus cell complex and that the inhibitor-induced changes in metabolism are consistent with the presumed mechanism of action of each inhibitor. In addition, whereas metabolism favors conversion of IMP to adenyl nucleotides, synthesis of adenyl nucleotides by this route during the culture period is apparently not required for hypoxanthine-maintained meiotic arrest in vitro.
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PMID:High performance liquid chromatography analysis of hypoxanthine metabolism in mouse oocyte-cumulus cell complexes: effects of purine metabolic perturbants. 808 Sep 28


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