Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.17.3.2 (xanthine oxidase)
 8,383 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pathways producing and converting adenosine have hardly been investigated in human heart, contrasting work in other species. We compared the kinetics of enzymes associated with purine degradation and salvage in human and rat heart cytoplasm assaying for adenosine deaminase, nucleoside phosphorylase, xanthine oxidoreductase, AMP deaminase, AMP- and IMP-specific 5'-nucleotidases, adenosine kinase and hypoxanthine guanine phosphoribosyltransferase (HGPRT). Xanthine oxidoreductase was not detectable in human heart. The Km-values of the AMP-catabolizing enzymes were 2-5 times higher in human heart; the substrate affinity of the other enzymes was in the same order of magnitude in both species. The maximal activity (Vmax) of adenosine kinase was the same in both species, but HGPRT in man was only 12% of that in the rat. For human heart the Vmax-values of adenosine deaminase, nucleoside phosphorylase, AMP- and IMP-specific 5'-nucleotidases, and AMP deaminase were 25-50% of those for rat heart. We conclude that human heart is less geared to purine catabolism than rat heart as is evident from the lower activities of the catabolic enzymes. Maintenance of the nucleotide pool may thus play a more important role in human heart.
 ...
PMID:Kinetics of adenylate metabolism in human and rat myocardium. 759 55

To determine whether interferon-gamma affects rat purine catabolic and salvage enzyme activities, rats were injected with interferon-gamma (600000 U/kg, i.p.) and, similarly to a vehicle-injected control group, killed before or after injection at 6, 12, and 24 h. Organ homogenates were prepared and enzymatic reactions with substrates were carried out, after which the products were measured either chromatographically or spectrophotometrically. Western and Northern blotting also were performed. In contrast to the vehicle-injected rats, interferon-gamma-injected rats showed a significant rise in xanthine oxidoreductase activity in the liver, while enzyme activity was unchanged in the spleen, kidney, and lung. Western analysis of hepatic xanthine oxidoreductase showed an increased concentration of this protein 12 and 24 h after interferon-gamma injection. Northern analysis disclosed an enhanced mRNA expression coding for this enzyme, peaking 12 h after injection. Contrastingly, the activities of adenosine deaminase, purine nucleoside phosphorylase, hypoxanthine guanine phosphoribosyltransferase, and adenine phosphoribosyltransferase were not affected by interferon-gamma in any organ tested. While interferon-gamma causes an increased hepatic biosynthesis of xanthine oxidoreductase, the physiologic role of this enzyme induction remains undetermined.
 ...
PMID:Effect of interferon-gamma on purine catabolic and salvage enzyme activities in rats. 1035 Jun 54

To examine the effect of 2-(3-cyano-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylic acid (TEI-6720), an inhibitor of xanthine oxidase, on purine metabolism in the lung cancer cell line A549, the activities of adenosine deaminase, purine nucleoside phosphorylase, adenine phosphoribosyltransferase, hypoxanthine guanine phosphoribosyltransferase, xanthine oxidase, and guanase together with pyrimidine nucleoside phosphorylase were measured with or without the addition of TEI-6720, and the extracellular concentrations of hypoxanthine, xanthine, inosine, uracil, and uridine were measured after the addition of inosine or uridine to the incubation medium with or without TEI-6720. Moreover, the Na-independent nucleoside transport was determined in A549 cells with or without TEI-6720. TEI-6720 inhibited the activity of xanthine oxidase in A549 cells, but did not affect other enzymes. During incubation, TEI-6720 not only prevented a decrease in the inosine concentration in inosine-containing medium, but also a decrease in the uridine concentration in uridine-containing medium. Furthermore, the Na-independent transport of uridine was inhibited by TEI-6720 with a K(i) value of 4.1 micromol/l. These results indicate that TEI-6720 is an inhibitor of the Na-independent nucleoside transport of uridine and inosine, as well as xanthine oxidase.
 ...
PMID:Effect of TEI-6720, a xanthine oxidase inhibitor, on the nucleoside transport in the lung cancer cell line A549. 1062 41