Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.4.4 (adenosine deaminase)
 5,136 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The adenosine uptake blocker propentofylline (HWA 285) has previously been shown to protect hippocampal CA1 pyramidal cells from ischaemia-induced delayed neuronal death. The influence of propentofylline, on the extracellular concentrations of purines, aspartate and glutamate in the CA1 of the rat hippocampus during transient forebrain ischaemia was investigated. 2. Twenty min of ischaemia was induced by four-vessel occlusion in Wistar rats, extracellular compounds were sampled by use of microdialysis and EEG was recorded by a tungsten electrode attached to the dialysis probe. 3. Propentofylline (10 mg kg-1 i.p.) did not influence the basal levels of any of the compounds in the hippocampal dialysates. 4. The EEG became isoelectric within 20 s after induction of ischaemia. 5. Extracellular adenosine, inosine, hypoxanthine, aspartate and glutamate increased several fold during ischaemia and remained elevated during early reflow. Within 2 h of reperfusion the concentration of all compounds was normalized. Xanthine increased upon reperfusion and remained elevated after 2 h. 6. Propentofylline (10 mg kg-1 i.p.) administered 15 min before ischaemia significantly enhanced the ischaemia-evoked increase of adenosine but attenuated the increases of the other purine catabolites and of glutamate. 7. In separate in vitro experiments, propentofylline did not inhibit adenosine deaminase activity. 8. The present data show that propentofylline enhances extracellular adenosine and lowers extracellular glutamate in vivo during ischaemia. These findings may be important in relation to the neuroprotective properties of propentofylline.
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PMID:Effect of propentofylline (HWA 285) on extracellular purines and excitatory amino acids in CA1 of rat hippocampus during transient ischaemia. 220 1

Previous studies have shown that activation of A1 and A2 adenosine receptors leads to inhibition and stimulation respectively of renin secretion by rat renal cortical slices. In the present studies, rat renal cortical slices were incubated in the presence of adenosine deaminase, to destroy any adenosine released from the preparation. N6-cyclohexyladenosine (CHA) had a biphasic effect on renin secretion: submicromolar concentrations inhibited concentration-dependently, and there was an inflection in the dose-response curve near 1 microM CHA such that higher concentrations produced a concentration-dependent relative stimulation, which became an absolute stimulation (i.e., secretory rate was higher than control) at 50 microM. These findings are consistent with A1 and A2 adenosine receptor-mediated inhibition and stimulation of renin secretion, respectively. Xanthine amine congener ["XAC," 8-(4-((2-aminoethyl)-aminocarbonylmethyloxy)phenyl-1,3-dipropyl xant hine] has been shown by others to be a very potent adenosine receptor antagonist with selectivity for A1 receptors. It antagonized both CHA-induced inhibition (Ki approximately 2 x 10(-9) M) and CHA-induced stimulation (Ki approximately 5 x 10(-8) M) of renin secretion. Thus, XAC exhibited a 25-fold selectivity for CHA-induced inhibition of renin secretion in comparison with CHA-induced stimulation. In comparison with previous results, XAC is approximately 3 orders of magnitude more potent than theophylline. In conclusion, occupation of adenosine receptors can lead either to inhibition (A1 receptor-mediated) or stimulation (A2 receptor-mediated) of renin secretion, and XAC is a very potent and selective antagonist of CHA-induced changes in renin secretion.
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PMID:XAC, a functionalized congener of 1,3-dialkylxanthine, antagonizes A1 adenosine receptor-mediated inhibition of renin secretion in vitro. 332 70

To find general metabolic profiles of purine ribo- and deoxyribonucleotides in potato (Solanum tuberosum L.) plants, we looked at the in situ metabolic fate of various (14)C-labelled precursors in disks from growing potato tubers. The activities of key enzymes in potato tuber extracts were also studied. Of the precursors for the intermediates in de novo purine biosynthesis, [(14)C]formate, [2-(14)C]glycine and [2-(14)C]5-aminoimidazole-4-carboxyamide ribonucleoside were metabolised to purine nucleotides and were incorporated into nucleic acids. The rates of uptake of purine ribo- and deoxyribonucleosides by the disks were in the following order: deoxyadenosine > adenosine > adenine > guanine > guanosine > deoxyguanosine > inosine > hypoxanthine > xanthine > xanthosine. The purine ribonucleosides, adenosine and guanosine, were salvaged exclusively to nucleotides, by adenosine kinase (EC 2.7.1.20) and inosine/guanosine kinase (EC 2.7.1.73) and non-specific nucleoside phosphotransferase (EC 2.7.1.77). Inosine was also salvaged by inosine/guanosine kinase, but to a lesser extent. In contrast, no xanthosine was salvaged. Deoxyadenosine and deoxyguanosine, was efficiently salvaged by deoxyadenosine kinase (EC 2.7.1.76) and deoxyguanosine kinase (EC 2.7.1.113) and/or non-specific nucleoside phosphotransferase (EC 2.7.1.77). Of the purine bases, adenine, guanine and hypoxanthine but not xanthine were salvaged for nucleotide synthesis. Since purine nucleoside phosphorylase (EC 2.4.2.1) activity was not detected, adenine phosphoribosyltransferase (EC 2.4.2.7) and hypoxanthine/guanine phosphoribosyltransferase (EC 2.4.2.8) seem to play the major role in salvage of adenine, guanine and hypoxanthine. Xanthine was catabolised by the oxidative purine degradation pathway via allantoin. Activity of the purine-metabolising enzymes observed in other organisms, such as purine nucleoside phosphorylase (EC 2.4.2.1), xanthine phosphoribosyltransferase (EC 2.4.2.22), adenine deaminase (EC 3.5.4.2), adenosine deaminase (EC 3.5.4.4) and guanine deaminase (EC 3.5.4.3), were not detected in potato tuber extracts. These results suggest that the major catabolic pathways of adenine and guanine nucleotides are AMP --> IMP --> inosine --> hypoxanthine --> xanthine and GMP --> guanosine --> xanthosine --> xanthine pathways, respectively. Catabolites before xanthosine and xanthine can be utilised in salvage pathways for nucleotide biosynthesis.
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PMID:Profiles of purine biosynthesis, salvage and degradation in disks of potato (Solanum tuberosum L.) tubers. 1684 29