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)

1. Enzymological and metabolic data in a patient with nucleoside phosphorylase (NP) deficiency are described. 2. Incubation of intact NP-deficient red cells with [14C]adenosine showed a rapid uptake and conversion to inosine. Almost no radioactivity was incorporated in the adenosine nucleotides and no hypoxanthine labeling could be detected. 3. Incubation with [14C]inosine resulted in a rapid conversion to IMP in the normal intact red cells but in an accumulation of inosine in the medium with the erythrocytes of the patient, proving again that a NP deficiency is present. 4. The high PRPP level found may result from impaired consumption due to lack of substrates for the salvage enzyme HGPRT. 5. Incubation with [14C]hypoxanthine and [14C]adenine showed that normal HGPRT and APRT activities were present in the NP-deficient red cells. 6. In serum and urine of the patient the levels of inosine and guanosine were considerably increased, while the serum and urinary levels of uric acid were very low. In the two deceased sisters NP deficiency was also strongly suggested by analyses of the serum purines, of stored deep frozen samples.
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PMID:A patient with purine nucleoside phosphorylase deficiency: enzymological and metabolic aspects. 40 97

Love, Samuel H. (Bowman Gray School of Medicine, Wake Forest College, Winston-Salem, N.C.), and Charles N. Remy. Metabolism of methylated purines in Escherichia coli: derepression of purine biosynthesis. J. Bacteriol. 91:1037-1049. 1966.-Various methylated purines were examined for their effects on growth of purine-requiring mutants of Escherichia coli, strains W-11 and B-96, and for their effects on purine biosynthesis. 6-Methylaminopurine and 6-methoxypurine stimulated the accumulation of purine precursor derivatives (ribosyl-5-aminoimidazole and ribosyl-5-amino-4-imidazole carboxamide) beyond their ability to support growth. Information obtained from in vivo and in vitro systems demonstrated that the metabolism of 6-methylaminopurine and 6-methoxypurine utilized identical pathways. The riboside derivatives are formed either by direct ribosidation via nucleoside phosphorylase or, indirectly, by dephosphorylation of the 5'-phosphoribosyl derivatives which are synthesized via adenylate pyrophosphorylase. Information obtained with the aid of strain W-11/DAP (lacking adenylate pyrophosphorylase) demonstrated that both pathways were important to the growing cells. Regardless of the metabolic pathway by which they are synthesized, the ribosyl derivatives are demethylaminated (demethylated) by adenosine deaminase to yield inosine. The final conversion of inosine to inosinic acid via the intermediate formation of hypoxanthine accounts for the net conversion of the methylated bases to inosinic acid. The utilization of the bases is sufficiently rate-limiting to cause derepression of the early enzymes required for the de novo synthesis of purine, thus accounting for the elevated accumulation of purine precursors originally observed.
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PMID:Metabolism of methylated purines in Escherichia coli: derepression of purine biosynthesis. 532 92

The erythrocyte adenosine deaminase, nucleoside phosphorylase, hypoxanthineguanine phosphoribosyltransferase and adenine phosphoribosyltransferase activities and plasma urate concentrations were measured in 20 cases of Down's syndrome and in 20 age- and sex-matched control subjects. The mean erythrocyte adenosine deaminase and adenine phosphoribosyltransferase activities and plasma urate concentrations were significantly higher in Down's syndrome subjects than in controls (p less than 0.001, p less than 0.01 and p less than 0.001, respectively). In all subjects studied there was a positive correlation between the erythrocyte adenosine deaminase activity and plasma urate concentration (r = 0.488, p less than 0.005). The concentrations of the erythrocyte adenine nucleotides, AMP, ADP and ATP, did not differ in Down's syndrome (n = 10) from those of control subjects (n = 10). The results suggest that the increase of plasma urate concentrations is a consequence of the increase in adenosine deaminase activity in Down's syndrome patients.
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PMID:Erythrocyte adenosine deaminase, purine nucleoside phosphorylase and phosphoribosyltransferase activity in patients with Down's syndrome. 621 25

Chromosomal aberrations in human gliomas are principally numerical. In tumours of low malignancy, karyotypes are frequently normal, but occasionally an excess of chromosome 7 and a loss of sex chromosome are observed. In highly malignant tumours, the most frequent aberrations are gain of chromosome 7, loss of chromosome 10 and less frequently losses or deletions of chromosomes 9, 22, 6, 13 and 14 or gains of chromosomes 19 and 20. To understand the meaning of these chromosome imbalances, the relationships between chromosome abnormalities and metabolic disturbances were studied. The losses or deletions observed affected principally chromosomes carrying genes encoding enzymes involved in purine metabolism. The activities of ten enzymes were measured: adenosine kinase, adenine phosphoribosyltransferase, adenylate kinase, methylthioadenosine phosphorylase, hypoxanthine phosphoribosyltransferase, adenylosuccinate lyase, inosine monophosphate dehydrogenase, adenosine deaminase, nucleoside phosphorylase and adenosine monophosphate deaminase. In parallel, two enzymes involved in pyrimidine metabolism, thymidine kinase and thymidylate synthase (TS), were studied. The activities of all these enzymes were measured on samples from 30 human primary glial tumours with low or high malignancy, six xenografted tumours at different passages, four portions of normal brain tissue and four non-glial brain neoplasms. As suggested by cytogenetic data, the enzymatic results showed a relatively low activity of purine metabolism in glial tumours when compared with normal brain and non-glial brain neoplasms. Considering the two enzymes involved in pyrimidine metabolism, only TS had higher activity in glial tumours of high malignancy than in normal brain. In comparison with normal brain, the balance between salvage and de novo pathways changes in gliomas, and even more in grafted tumours, in favour of de novo synthesis. The relation between chromosomes and metabolic imbalances does not correspond to a simple gene dosage effect in these tumours. These data suggest that the decrease of adenosine metabolism occurs before chromosomal aberrations appear, since it is observed in tumours of low malignancy when most karyotypes are still normal, and that the de novo pathway increases with tumour progression.
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PMID:Purine and pyrimidine metabolism in human gliomas: relation to chromosomal aberrations. 805 68