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)

Xanthine dehydrogenase has been purified from Pseudomonas aeruginosa cultured on a rich medium and induced with hypoxanthine. The enzyme was shown to contain FAD, iron sulfur centers and a molybdenum cofactor as prosthetic groups. Analysis of the molybdenum cofactor in this enzyme has revealed that the cofactor contains molybdopterin (MPT) rather than molybdopterin guanine dinucleotide or molybdopterin cytosine dinucleotide which have previously been identified in a number of molybdoenzymes of bacterial origin. The pterin cofactor in P.aeruginosa xanthine dehydrogenase was alkylated and the resulting product was identified as dicarboxamidomethyl molybdopterin. In addition, the pterin released from the enzyme by denaturation with guanidine-HCl was found to chromatograph on Sephadex G-15 with an apparent molecular weight of 350. These results document the first example of a bacterial enzyme with a molybdenum cofactor comprising molybdopterin and the metal only.
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PMID:Identification of a molybdopterin-containing molybdenum cofactor in xanthine dehydrogenase from Pseudomonas aeruginosa. 165 22

In the systemic circulation, LDL occurs in the form of a weakly nitrated LDL-albumin complex (LAC). The question here is whether LAC (or HDL) is able to denitrate the albumin-bound 3-NO(2)-tyrosine (3NT). Nitrated albumin was incubated in the presence of lipoprotein fraction (LPF) to be tested, with or without Ca(2+). After precipitation and centrifugation, supernatants (SNs) and protein pellets (PP) were collected. HCl proteolysis was carried out with deuterated 3NT as an internal standard, and amino acids were derivatized for GC-MS analysis, whereas SNs were used for NO(2) (-)/NO(3) (-)-fluorimetric assays. A loss of 3NT, higher with albumin-low LDL than with albumin-rich LDL or HDL, was found in PP only in the presence of Ca(2+). gamma-Tocopherol loading of LPF inhibited 3NT loss. 3NT loss was found for the first time to be stoichiometrically equivalent to NO(3) (-), proving that the 3NT loss must be ascribed to a 3NT-denitrating nitratase activity. 3NT loss and NO(3) (-) production that clearly cannot be attributed to PON-1 were impaired by D-penicillamine and phenylacetate, inhibitor, and substrate of PON-1, respectively, leading to speculate on the active site. Finally, nitratase activity and albumin contribute to beneficially convert peroxynitrite (ONOO(-)) into nonbioactive NO(3) (-). But, in inflammatory conditions, xanthine oxidoreductase is expressed leading to detrimentally reduce O(2) and NO(3) (-) into O(2) (*) (-) and NO(*) that may interact, reconstituting the ONOO(-) pool. The real consequence of nitratase activity and the physiological significance of nitration/denitration processes remain to be explored.
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PMID:First evidence for an LDL- and HDL-associated nitratase activity that denitrates albumin-bound nitrotyrosine--physiological consequences. 1837 95

Mammalian xanthine oxidoreductase can be converted from the dehydrogenase to the oxidase form, either reversibly by formation of disulfide bridges or irreversibly by proteolytic cleavage within the xanthine oxidoreductase protein molecule. A tightly packed amino acid cluster stabilizes the dehydrogenase form, and disruption of this cluster is accompanied with rearrangement of the active site loop. Here, we show that the conversion occurs in the presence of guanidine-HCl or urea. We propose that xanthine dehydrogenase and oxidase are in a thermodynamic equilibrium that can be shifted by disruption of the amino acid cluster with a denaturant.
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PMID:Mechanism of transition from xanthine dehydrogenase to xanthine oxidase: effect of guanidine-HCL or urea on the activity. 1860 May 57