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)

Xanthine dehydrogenase (XD) is a key enzyme in the catabolism of purines. A recently isolated XD cDNA clone (Terao et al., Biochem. J. 283, 863-870, 1992) was used to analyze the genomic structure and chromosomal location of this gene. XD was found to be a single-copy gene approximately 70 kb long with 36 exons containing the transcribed sequence. The length of the mouse XD gene was much longer and the structure more complex than those of the Drosophila and Calliphora homologs. The locus encoding the XD gene (designated Xd) was mapped to the distal part of mouse chromosome 17 by haplotype analysis of 114 interspecific backcross mice. Although Xd inactivation may be responsible for xanthinuria, a rare human genetic disease, this genetic locus is not a candidate for any previously described mouse mutation. The transcription start site was defined by primer extension and RNase mapping analysis, using liver mRNA. No other transcription start sites were identified in the liver and a variety of other organs after treatment with an interferon inducer. Transient transfection analysis in NIH3T3, tEnd, and COS cells with an appropriate reporter gene demonstrated that a functional promoter is located within the first 268 bp preceding the transcriptional initiation site.
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PMID:Chromosomal mapping, isolation, and characterization of the mouse xanthine dehydrogenase gene. 783 88

To study the expression of human xanthine dehydrogenase/oxidase (hXDH/XO), we cloned the cDNA covering its complete coding sequence and characterized it by translation in vitro in rabbit reticulocyte lysates and by transient expression in COS-1 cells. Two specific protein products with approximate molecular masses of 150 and 130 kDa were detected in both expression systems. These products are compatible with the molecular sizes of XDH/XO, and these peptides also showed immunoreactivity with polyclonal anti-hXDH antibodies. Significant XDH/XO enzyme activity (277 +/- 54 pmol/min per mg of protein) was measured in lysates of transfected COS cells, whereas in control transfections the activities were below the detection limit of our assay (0.2 pmol/min per mg of protein). The COS cells expressed the enzyme predominantly (89.8 +/- 0.3%) in the dehydrogenase form.
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PMID:Cloning and expression in vitro of human xanthine dehydrogenase/oxidase. 867 Jan 12

Our previous studies show that 10 xanthine oxidase (XO) variants (Arg149Cys, Pro555Ser, Arg607Gln, Thr623Ile, Ile703Val Asn909Lys, Thr910Lys, Pro1150Arg, His1221Arg, and Cys1318Tyr) exhibit altered activity toward the endogenous substrate xanthine. This study investigates whether these variants also exhibit altered kinetics for the exogenous substrate 6-thioxanthine (6-TX). To investigate the kinetics of wild-type XO and these variants, expression constructs were transfected into mammalian COS-7 cells. S-9 fractions containing the expressed proteins were used to determine their kinetic parameters, i.e., K(m), V(max), and intrinsic clearance (CL(int)), for the substrate 6-TX. Functional characterization of the 10 XO variants revealed that 4 of the variants (Arg149Cys, Asn909Lys, Thr910Lys, and Pro1150Arg) were inactive, 2 (Arg607Gln, and Cys1318Tyr) had reduced activity (CL(int), 55.5% and 64.7% less than that of wild-type XO, respectively). This study provides comprehensive data regarding how genetic variation in XO affects its activity toward 6-TX. We found that the in vitro activity of 8 of the XO variants toward 6-TX was functionally affected. These results suggeste that polymorphism in the gene encoding XO may increase the toxicity of thiopurine drugs such as 6-mercaputopurine.
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PMID:Kinetics of 6-thioxanthine metabolism by allelic variants of xanthine oxidase. 2081 57