Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.17.1.4 (xanthine dehydrogenase)
 1,236 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The constitutive xanthine dehydrogenase and the inducible 2-furoyl-coenzyme A (CoA) dehydrogenase could be labeled with [185W]tungstate. This labeling was used as a reporter to purify both labile proteins. The radioactivity cochromatographed predominantly with the residual enzymatic activity of both enzymes during the first purification steps. Both radioactive proteins were separated and purified to homogeneity. Antibodies raised against the larger protein also exhibited cross-reactivity toward the second smaller protein and removed xanthine dehydrogenase and 2-furoyl-CoA dehydrogenase activity up to 80 and 60% from the supernatant of cell extracts, respectively. With use of cell extract, Western immunoblots showed only two bands which correlated exactly with the activity stains for both enzymes after native polyacrylamide gel electrophoresis. Molybdate was absolutely required for incorporation of 185W, formation of cross-reacting material, and enzymatic activity. The latter parameters showed a perfect correlation. This evidence proves that the radioactive proteins were actually xanthine dehydrogenase and 2-furoyl-CoA dehydrogenase. The apparent molecular weight of the native xanthine dehydrogenase was about 300,000, and that of 2-furoyl-CoA dehydrogenase was 150,000. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of both enzymes revealed two protein bands corresponding to molecular weights of 55,000 and 25,000. The xanthine dehydrogenase contained at least 1.6 mol of molybdenum, 0.9 ml of cytochrome b, 5.8 mol of iron, and 2.4 mol of labile sulfur per mol of enzyme. The composition of the 2-furoyl-CoA dehydrogenase seemed to be similar, although the stoichiometry was not determined. The oxidation of furfuryl alcohol to furfural and further to 2-furoic acid by Pseudomonas putida Fu1 was catalyzed by two different dehydrogenases.
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PMID:Xanthine dehydrogenase and 2-furoyl-coenzyme A dehydrogenase from Pseudomonas putida Fu1: two molybdenum-containing dehydrogenases of novel structural composition. 217 Mar 35

2,5-Diaziridinyl-3-(hydroxymethyl)-6-methyl-1,4-benzoquinone (RH1) is a novel antitumor diaziridinyl benzoquinone derivative designed to be bioactivated by the two-electron reductase NAD(P)H:quinone oxidoreductase (NQO1) and is currently in clinical trials. NQO1 is expressed at high levels in many solid tumors. RH1 cytotoxicity has been shown previously to be NQO1-dependent. The purpose of this study was to investigate whether other reducing enzymes such as cytochrome b(5) reductase (b5R), cytochrome P450 reductase (P450R), dihydronicotinamide riboside:quinone oxidoreductase 2 (NQO2), and xanthine oxidase/xanthine dehydrogenase (XO/XDH) also contribute to the bioactivation and cytotoxicity of RH1 in human tumor cells. For these studies, we established a series of stable MDA468 breast cancer cell lines overexpressing various levels of NQO1, b5R, P450R, and NQO2 and compared RH1-induced growth inhibition [3-(4,5-dimethylthiazol-2,5-diphenyl)tetrazolium and sulforhodamine B analysis] and interstrand DNA cross-linking (comet analysis) in both parental MDA468 cells and transfected clones. RH1 toxicity correlated with NQO1 and NQO2 but not with either b5R or P450R activity levels in the respective series of transfected MDA468 cell clones. Enzymatic assays showed that RH1 was an in vitro substrate for xanthine oxidase. However, XO/XDH protein and activity could not be detected in a variety of human tumor cell lines. These studies suggest that NQO1 and NQO2 are the principal enzymatic determinants of RH1 bioactivation in MDA468 tumor cells and that b5R, P450R, and XDH/XO are unlikely to play major roles. Our studies also suggest that NQO2 may be particularly relevant as a bioactivation system for RH1 in NQO1-deficient tumors such as leukemias and lymphomas.
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PMID:Dissecting the role of multiple reductases in bioactivation and cytotoxicity of the antitumor agent 2,5-diaziridinyl-3-(hydroxymethyl)-6-methyl-1,4-benzoquinone (RH1). 1879 27

The mitochondrial amidoxime reducing component mARC is a newly discovered molybdenum enzyme that is presumed to form the catalytical part of a three-component enzyme system, consisting of mARC, heme/cytochrome b(5), and NADH/FAD-dependent cytochrome b(5) reductase. mARC proteins share a significant degree of homology to the molybdenum cofactor-binding domain of eukaryotic molybdenum cofactor sulfurase proteins, the latter catalyzing the post-translational activation of aldehyde oxidase and xanthine oxidoreductase. The human genome harbors two mARC genes, referred to as hmARC-1/MOSC-1 and hmARC-2/MOSC-2, which are organized in a tandem arrangement on chromosome 1. Recombinant expression of hmARC-1 and hmARC-2 proteins in Escherichia coli reveals that both proteins are monomeric in their active forms, which is in contrast to all other eukaryotic molybdenum enzymes that act as homo- or heterodimers. Both hmARC-1 and hmARC-2 catalyze the N-reduction of a variety of N-hydroxylated substrates such as N-hydroxy-cytosine, albeit with different specificities. Reconstitution of active molybdenum cofactor onto recombinant hmARC-1 and hmARC-2 proteins in the absence of sulfur indicates that mARC proteins do not belong to the xanthine oxidase family of molybdenum enzymes. Moreover, they also appear to be different from the sulfite oxidase family, because no cysteine residue could be identified as a putative ligand of the molybdenum atom. This suggests that the hmARC proteins and sulfurase represent members of a new family of molybdenum enzymes.
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PMID:Biochemical and spectroscopic characterization of the human mitochondrial amidoxime reducing components hmARC-1 and hmARC-2 suggests the existence of a new molybdenum enzyme family in eukaryotes. 2086 Oct 21