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

1. Rate sedimentation and isopycnic centrifugation were used to analyse the subcellular sites of enzymes in homogenates of goldfish intestinal mucosa. 2. The results allowed the following allocations to be made: carnitine acetyl transferase-mitochondrial and peroxisomal, xanthine dehydrogenase and NAD: alpha-glycerophosphate dehydrogenase soluble phase, NADP: isocitrate dehydrogenase soluble phase and mitochondrial, and 2-naphthyl laurate hydrolase microsomal and/or brush border. 3. Histochemistry confirmed the use of alkaline phosphatase and 1-naphthyl acetate esterase as brush border and microsome markers respectively. 4. Urate oxidase, allantoinase, allantoicase, xanthine oxidase and glycollate/lactate oxidase, activities were undetectable, and 1-naphthyl palmitate hydrolase was present only as a contaminant from pancreas.
 ...
PMID:Intestinal peroxisomes of goldfish (Carassius auratus)--examination for hydrolase, dehydrogenase and carnitine acetyltransferase activities. 31 95

The cnx- group of mutants of Aspergillus nidulans lacks xanthine dehydrogenase (xanthine: NAD+ oxidoreductase, EC 1.2.1.37) and nitrate reductase (EC 1.6.6.3) activities and are thought to be defective in the synthesis of a molybdenum-containing cofactor, 'cnx', common to xanthine dehydrogenase and nitrate reductase [Pateman, J.A., Rever, B.M., Cove, D.J. and Roberts, D.B. (1964) Nature (Lond.) 201, 58-60]. The cnx cofactor has a role in maintaining the aggregated multimeric structure of nitrate reductase [MacDonald, D.W., Cove, D.J. and Coddington, A. (1974) Mol. Gen. Genet. 128, 187-199]. We report here that, in cnx- mutants grown under conditions inducing xanthine dehydrogenase I, a species cross-reacting with antisera to the native enzyme and of half its molecular weight is present, together with cross-reacting molecules of similar molecular weight to the native enzyme. This suggests that the cnx cofactor has a role in maintaining the aggregated structure of xanthine dehydrogenase I. Both cross-reacting species are capable of passing reducing equivalents from NADH to a tetrazolium salt, showing that the cnx cofactor is not necessary for enzymic activity towards NADH.
 ...
PMID:The genetic control of molybdoflavoproteins in Aspergillus nidulans. A xanthine dehydrogenase I half-molecule in cnx- mutant strains of Aspergillus nidulans. 33 Jan 63

In Aspergillus nidulans uric acid can be produced from xanthine via purine hydroxylase I (xanthine dehydrogenase) or via the xanthine alternative pathway (Darlington and Scazzocchio, Biochem. Biophys. Acta, 166, 569--571; 1968). A mutation defective in the xanthine alternative pathway of Aspergillus nidulans is described. By combining this mutation with hxB-20 which results in complete loss of purine hydroxylase I and II activities, but which conserves cross-reacting material, it is possible to block completely uric acid production and thus investigate which are the effective in vivo inducers of three enzymes under the control of the positive regulatory gene uaY: adenine deaminase, purine hydroxylase I (measured as cross-reacting material) and urate oxidase. It is concluded that uric acid is the only effective physiological inducer, while its 2 and 8 thio-analogues serve as gratuitous inducers.
 ...
PMID:A mutation defective in the xanthine alternative pathway of Aspergillus nidulans: its use to investigate the specificity of uaY mediated induction. 36 58

A point mutation in the structural gene for purine hydroxylase I (xanthine dehydrogenase) of Aspergillus nidulans results in several dramatic pleiotropic effects. The mutant enzyme oxidises 2-hydroxypurine at position 6 rather than 8, shows a 70-fold reduction in the V for hypoxanthine, and loses the ability to accept xanthine as a substrate. Allopurinol, a powerful pseudoirreversible inhibitor of the wild type enzyme, behaves as a good substrate of the mutant enzyme. We propose that the substrate and inhibitor specificities of the enzymes depend on the relative position of an orientating site ann a catalytic site. All the properties of the mutant enzyme can be explained by assuming that the mutation results in a change of the relative positions of the catalytic and orientating sites. We have assumed that the catalytic site comprises a Mo(VI) atom and an--S-group as proposed by Coughlan [FEBS Lett. 81, 1--9 (1977)] and the orientating site is a lysyl residue. While these assumptions are not strictly necessary for the construction of an abstract geometric model, they are consistent with other data bearing on the structure of the active site of the molybdenum-containing hydroxylases.
 ...
PMID:A mutation in the xanthine dehydrogenase (purine hydroxylase I) of Aspergillus nidulans resulting in altered specificity. Implications for the geometry of the active site. 36 29

1. Adenine, hypoxanthine, xanthine and guanine are broken down in Pseudomonas aeruginosa and Pseudomonas testosteroni to allantoin by the concerted action of the enzymes adenine deaminase, guanine deaminase, NAD+-dependent xanthine dehydrogenase and uricase. 2. Uric acid is broken down by an unstable, membrane-bound uricase with an unusually low pH optimum. 3. In both strains adenine inhibits growth and xanthine dehydrogenase. A second type of inhibition is manifest only in Ps. testosteroni and concerns the regulation of the biosynthesis of amino acids of the aspartate family. Enzymic studies showed that in this strain aspartate kinase is inhibited by AMP.
 ...
PMID:Purine degradation in Pseudomonas aeruginosa and Pseudomonas testosteroni. 40 41

In the course of postnatal development from the hatching up to the age of 84 days, the activities of xanthine dehydrogenase (XDH), glutamate dehydrogenase (GLDH) and arginase were examined in the liver of Japanese quail. The observation in weekly intervals showed a gradual character of XDH development whereas the conclusion of the first degree correlated to some extent with the period of achieving the sexual maturity of animals. The GLDH activity increased in the course of the growth with attainment of the maximum value in the same period. The course of the development of hepatic arginase activity indicated the potential changes of this enzyme.
 ...
PMID:[Postnatal development of enzyme activities of nitrogen catabolism in the liver of Japanese quail]. 41 Dec 25

The effects of Vicia faba diet on urinary nitrogenous compounds and on enzyme activities of pathways directly associated with amino acid metabolism were studied in rats and chicks. The urea and creatinine excretion of rats fed on V. faba was approximately 90% more than that of control rats. The V.-faba-fed rats had increased activities of liver arginase (EC 3.5.3.1), argininosuccinate synthetase (EC 6.3.4.5) and alanine aminotransferase (EC 2.6.1.2). The chicks fed on V. faba also showed increased activity of xanthine dehydrogenase (EC 1.2.3.2). The possible nature of these altered amino-acid-degrading enzyme activities is discussed.
 ...
PMID:Effect of raw field bean (Vicia faba) on amino-acid-degrading enzymes in rats and chicks. 42 86

The present study describes the (xanthine:NAD+ oxidoreductase, EC 1.2.1.37) synthesis and degradation of chick liver xanthine dehydrogenase in vivo and in organ cultures. The results indicate that control of xanthine dehydrogenase activity is mediated by changes in the rate of enzyme synthesis, but that degradation rates are unaffected. The results also suggest that xanthine dehydrogenase synthesis occurs through a previously unreported intermediate. Detected in cultures of liver tissue, this intermediate apparently is not converted into an active enzyme. A model of synthesis and degradation for xanthine dehydrogenase proposes that the synthesis of the enzyme is proportional to messenger RNA and includes an inactive enzyme precursor and a second inactive intermediate prior to degradation. Integrated mathematical solutions describing the concentration of intermediates as a function of time can be found explicitly for simple models. The appendix to this paper extrapolates solutions for one-, two- and three-step models to generate a mathematical solution for an 'n'-step model containing 'n' intermediates. The rate constants in the solutions can be found experimentally.
 ...
PMID:Synthesis and degradation of xanthine dehydrogenase in chick liver. In vivo and in vitro studies. 44 41

Xanthine dehydrogenase (EC 1.2.1.37) was isolated from chicken livers and immobilized by adsorption to a Sepharose derivative, prepared by reaction of n-octylamine with CNBr-activated Sepharose 4B. Using a crude preparation of enzyme for immobilization it was observed that relatively more activity was adsorbed than protein, but the yield of immobilized activity increased as a purer enzyme preparation was used. As more activity and protein were bound, relatively less immobilized activity was recovered. This effect was probably due to blocking of active xanthine dehydrogenase by protein impurities. The kinetics of free and immobilized xanthine dehydrogenase were studied in the pH range 7.5-9.1. The Km and V values estimated for free xanthine dehydrogenase increase as the pH increase; the K'm and V values for the immobilized enzyme go through a minimum at pH 8.1. By varying the amount of enzyme activity bound per unit volume of gel, it was shown that K'm is larger than Km are result of substrate diffusion limitation in the pores of the support material. Both free and immobilized xanthine dehydrogenase showed substrate activation at low concentrations (up to 2 microM xanthine). Immobilized xanthine dehydrogenase was more stable than the free enzyme during storage in the temperature range of 4-50 degrees C. The operational stability of immobilized xanthine dehydrogenase at 30 degrees C was two orders of magnitude smaller than the storage stability, t 1/2 was 9 and 800 hr, respectively. The operational stability was, however, better than than of immobilized milk xanthine oxidase (t 1/2 = 1 hr). In addition, the amount of product formed per unit initial activity in one half-life, was higher for immobilized xanthine dehydrogenase than for immobilized xanthine oxidase. Unless immobilized milk xanthine oxidase can be considerable stabilized, immobilized chicken liver xanthine dehydrogenase is more promising for application in organic synthesis.
 ...
PMID:Kinetics and stability of immobilized chicken liver xanthine dehydrogenase. 48 18

The enzyme, xanthine dehydrogenase (XDH), has been examined in Ambystoma tigrinum nebulosum with respect to its role in pigmentation. It now seems probable that the melanoid gene (m) either codes directly for XDH or is somehow intimately connected with the normal function of this enzyme. Inhibition of XDH using the drug, allopurinol, results in animals which appear to be phenocopies of melanoid mutants as described for the Mexican axolotl (Ambystoma mexicanum). The effects of allopurinol in terms of specific pigmentary alterations were examined, and a new method for analyzing heterogeneous extracts of skin pigments (e.g., purines and pteridines) is presented. The significance of the link between XDH and melanism is discussed with emphasis on possible mechanisms of pigment induction and general applicability to biological systems.
 ...
PMID:Allopurinol-induced melanism in the tiger salamander (Ambystoma tigrinum nebulosum). 49 Jan 38


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>