| xanthine nucleotide | The monophosphoric ester of xanthosine. An intermediate in GMP biosynthesis. Synonym: xanthidylic acid, xanthine nucleotide, xanthylic acid. (05 Mar 2000) |
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| methyl xanthine | <chemical, drug> Naturally occurring purine alkaloids such as theobromine, theophylline and caffeine (trimethyl xanthine). They inhibit cAMP phosphodiesterase and thus cause an increase in the intracellular cAMP concentration. (18 Nov 1997) |
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| xanthine | <biochemistry> A purine, the starting point for purine degradation. Its methylated derivatives (theophylline, theobromine, caffeine) are potent cAMP phosphodiesterase inhibitors. (18 Nov 1997) |
| xanthine alkaloids | Alkaloids, which contain xanthine as their nitrogenous base. (12 Dec 1998) |
| xanthine bronchodilator | <pharmacology> A group of medications that work by a common mechanism to effect bronchodilation (open up air passages) in the lungs. Used in the treatment of asthma and related conditions. Examples include: theophylline, aminophylline and dyphylline. (27 Sep 1997) |
| xanthine dehydrogenase | <enzyme> An enzyme that catalyses the oxidation of xanthine in the presence of NAD+ to form urate and NADH. It acts also on a variety of other purines and aldehydes. Chemical name: Xanthine:NAD+ oxidoreductase Registry number: EC 1.1.1.204 (12 Dec 1998) |
| xanthine oxidase | <enzyme> Dehydrogenases involved in conversion of hypoxanthine to xanthine and xanthine to uric acid, as the final catabolism of purines. Deficient in the human disease xanthinuria. (18 Nov 1997) |
| xanthine ribonucleoside | 9-beta-d-ribosylxanthine;the deamination product of guanosine (O replacing -NH2). Synonym: xanthine ribonucleoside. Abbreviation: Xao (05 Mar 2000) |
| hypoxanthine-guanine-xanthine phosphoribosyltransferase | <enzyme> From tritrichomonas foetus; in contrast to EC 2.4.2.8, this enzyme also uses xanthine as substrate; mw 24 kD Registry number: EC 2.4.2.- Synonym: hgxprtase (26 Jun 1999) |
| desulfo xanthine dehydrogenase | <enzyme> Naturally occuring inactive form of xanthine dehydrogenase Registry number: EC 1.1.1.- (26 Jun 1999) |
| adenine nucleotide | A condensation product of adenosine and phosphoric acid; a nucleotide found among the hydrolysis products of all nucleic acids. 3'-Adenylic acid (adenosine 3'-monophosphate) and 5'-adenylic acid (adenosine 5'-monophosphate) differ in the place of attachment of the phosphoric acid to the d-ribose; deoxyadenylic acid differs in having H instead of OH at the 2' position of d-ribose. See: AMP. Synonym: adenine nucleotide. (05 Mar 2000) |
| adenine nucleotide translocase | <enzyme> Catalyses the exchange between endogenous and exogenous adenine nucleotides in mitochondria.ec 2.7.7.-. Registry number: EC 2.7.7.- (12 Dec 1998) |
| cyclic nucleotide | A nucleoside monophosphate in which the phosphoryl group is linked twice to the sugar moiety; e.g., adenosine 3',5'-cyclic monophosphate (cAMP). (05 Mar 2000) |
| cyclic nucleotide-regulated protein kinases | <enzyme> A group of enzymes that catalyses the phosphorylation of serine or threonine residues of proteins and is dependent on cyclic nucleotides. Registry number: EC 2.7.10.- (12 Dec 1998) |
| pyrimidine-5'-nucleotide nucleosidase | <enzyme> Also acts on some deoxyribonucleotides Registry number: EC 3.2.2.10 Synonym: pyr-5'-nt-nucleosidase (26 Jun 1999) |
| nicotinamide-nucleotide adenylyltransferase | <enzyme> An enzyme that catalyses reversibly the transfer of the adenylyl moiety of ATP to the phosphoryl group of nmn to form NAD+ and pyrophosphate. The enzyme is found predominantly in the nuclei and catalyses the final reaction in the major pathway for the biosynthesis of NAD in mammals. Chemical name: ATP:nicotinamide-nucleotide adenylyltransferase Registry number: EC 2.7.7.1 (12 Dec 1998) |