Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.7 (adenine phosphoribosyltransferase)
 692 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clinical and enzymatic studies on two brothers with severe deficiencies of erythrocyte hypoxanthineguanine phosphoribosyltransferase (HGPRTase) are described, and are compared with similar studies of a classical case of the Lesch-Nyhan syndrome from another family. The two brothers have no neurological abnormalities, only traces of erythrocyte HGPRTase, erythrocyte adenine phosphoribosyltransferase activities approaching the high levels found in the Lesch-Nyhan patient, and similarly raised plasma and urinary concentrations of uric acid. Despite these strong biochemical similarities between the three patients, there were wide differences in the clinical case histories. In both families the enzyme deficiency appeared to be inherited as an X-linked character through asymptomatic carrier females. The relationship of HGPRTase deficiencies to the Lesch-Nyhan syndrome is discussed. Some observations relating to techniques are reported. Cellulose acetate has been found to give much better separations of labelled reaction products in low-level phosphoribosyltransferase assays than filter paper, when used as a supporting medium for electrophoresis. The analysis of hair follicles gives indications of individuals heterozygous for the enzyme deficiency, but the proportion of enzyme-deficient follicles was very small, and the test needs support from studies of other cell types. Using haemolysates, there were signs of a slow indirect conversion of hypoxanthine to inosinic acid, via inosine. Inosine appears to be labelled by a ribosyl-transfer reaction.
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PMID:Clinical and biochemical observations on three cases of hypoxanthine-guanine phosphoribosyltransferase deficiency. 115 84

Bacillus subtilis mutants defective in purine metabolism have been isolated by selecting for resistance to purine analogs. Mutants resistant to 2-fluoroadenine were found to be defective in adenine phosphoribosyltransferase (apt) activity and slightly impaired in adenine uptake. By making use of apt mutants and mutants defective in adenosine phosphorylase activity, it was shown that adenine deamination is an essential step in the conversion of both adenine and adenosine to guanine nucleotides. Mutants resistant to 8-azaguanine, pbuG mutants, appeared to be defective in hypoxanthine and guanine transport and normal in hypoxanthine-guanine phosphoribosyltransferase activity. Purine auxotrophic pbuG mutants grew in a concentration-dependent way on hypoxanthine, while normal growth was observed on inosine as the purine source. Inosine was taken up by a different transport system and utilized after conversion to hypoxanthine. Two mutants resistant to 8-azaxanthine were isolated: one was defective in xanthine phosphoribosyltransferase (xpt) activity and xanthine transport, and another had reduced GMP synthetase activity. The results obtained with the various mutants provide evidence for the existence of specific purine base transport systems. The genetic lesions causing the mutant phenotypes, apt, pbuG, and xpt, have been located on the B. subtilis linkage map at 243, 55, and 198 degrees, respectively.
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PMID:Genetic and physiological characterization of Bacillus subtilis mutants resistant to purine analogs. 311 Jan 31

Contribution of the adenine, adenosine and inosine salvage to the purine nucleotide and nucleic acid biosynthesis during white spruce (Picea glauca) somatic embryo maturation was estimated by in situ assays using [8-(14)C]adenine, [8-(14)C]adenosine and [8-(14)C]inosine. The salvage of adenine and adenosine was high during the initial stages of embryo maturation, characterized by rapid cell proliferation, but it declined upon further embryo development. Inosine salvage activity was always much lower than that observed for adenine and adenosine. Consistent with these results, activities of adenine phosphoribosyltransferase (APRT) and adenosine kinase (AK) measured in the embryo extracts in vitro were much higher than the activity of inosine kinase (IK) during all stages of embryo development. Utilization of adenosine and inosine for nucleotide and nucleic acid synthesis was found to be regulated by the enzymes AK and IK, as the pattern of their activities was very similar to the activity of adenosine and inosine salvage, estimated with exogenously supplied precursors. However, little correlation between salvage of adenine and activity of APRT was found throughout somatic embryo maturation. As no adenosine nucleosidase activity was found in white spruce embryos, adenosine, but not adenine, seems to be the major end product of adenylate catabolism and becomes the predominant substrate for purine salvage in vivo. Thus, adenosine salvage appeared to have the most important role in white spruce embryos. Studies on the metabolic fate of [8-(14)C]adenine and [8-(14)C]adenosine suggest that turnover of adenine nucleotides is rapid, as some of them are utilized for nucleic acid synthesis. In contrast, most of [8-(14)C]inosine taken up by the embryos seems to be directly catabolized by the conventional purine catabolic pathway via ureides in all stages of embryo maturation.
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PMID:Purine metabolism during white spruce somatic embryo development: salvage of adenine, adenosine, and inosine. 1144 40

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

To determine the metabolic profiles of purine nucleotides and related compounds in leaves and roots of tea (Camellia sinensis), we studied the in situ metabolic fate of 10 different (14)C-labeled precursors in segments from tea seedlings. The activities of key enzymes in tea leaf extracts were also investigated. The rates of uptake of purine precursors were greater in leaf segments than in root segments. Adenine and adenosine were taken up more rapidly than other purine bases and nucleosides. Xanthosine was slowest. Some adenosine, guanosine and inosine was converted to nucleotides by adenosine kinase and inosine/guanosine kinase, but these compounds were easily hydrolyzed, and adenine, guanine and hypoxanthine were generated. These purine bases were salvaged by adenine phosphoribosyltransferase and hypoxanthine/guanine phosphoribosyltransferase. Salvage activity of adenine and adenosine was high, and they were converted exclusively to nucleotides. Inosine and hypoxanthine were salvaged to a lesser extent. In situ (14)C-tracer experiments revealed that xanthosine and xanthine were not salvaged, although xanthine phosphoribosyltransferase activity was found in tea extracts. Only some deoxyadenosine and deoxyguanosine was salvaged and utilized for DNA synthesis. However, most of these deoxynucleosides were hydrolyzed to adenine and guanine and then utilized for RNA synthesis. Purine alkaloid biosynthesis in leaves is much greater than in roots. In situ experiments indicate that adenosine, adenine, guanosine, guanine and inosine are better precursors than xanthosine, which is a direct precursor of a major pathway of caffeine biosynthesis. Based on these results, possible routes of purine metabolism are discussed.
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PMID:Profiles of purine metabolism in leaves and roots of Camellia sinensis seedlings. 2107 29