Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.4.2.8 (hypoxanthine-guanine phosphoribosyltransferase)
2,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The activities of a number of purine metabolizing enzymes of erythrocytes and lymphocytes were determined in 18 subjects with Down's syndrome and in 18 age- and sex-matched control subjects. An increase of adenosine deaminase activity (adenosine or deoxyadenosine as substrates) was found in erythrocytes (P less than 0.001) as well as in lymphocytes (P less than 0.001) of Down's syndrome subjects compared to controls. The purine nucleoside phosphorylase activities in lymphocytes and plasma urate concentrations were also significantly higher in Down's syndrome subjects than in controls (P less than 0.001 and less than 0.02, respectively). Adenine phosphoribosyltransferase activities and hypoxanthine-guanine phosphoribosyltransferase activities in lymphocytes were identical in the two groups. In all subjects studied there were positive correlations between the erythrocyte adenosine deaminase activities, lymphocyte adenosine deaminase or deoxyadenosine activities, and plasma urate concentrations (P less than 0.05 in all cases), and between lymphocyte nucleoside phosphorylase and lymphocyte adenosine deaminase or deoxyadenosine deaminase activities (P less than 0.01 and less than 0.05, respectively). The results suggest that increased activities of some purine metabolizing enzymes found in both erythrocytes and lymphocytes may contribute to increased purine degradation and hyperuricemia in subjects with Down's syndrome. In addition, the increased adenosine deaminase and nucleoside phosphorylase activities may be related to the immunological dysfunction found in subjects with Down's syndrome.
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PMID:Levels of some purine metabolizing enzymes in lymphocytes from patients with Down's syndrome. 294 6

Ten cases of Lesch-Nyhan syndrome have been followed for 3-19 years (mean, 11 years and four months). Criteria of Lesch-Nyhan syndrome were restricted to the following: complete absence of hypoxanthine-guanine phosphoribosyltransferase (HPRT) in hemolysate and fibroblast, spasticity, choreoathetosis, mental retardation, self-mutilation, and occurrence in males. Two patients have died of pneumonia and two died suddenly. However, autopsies produced no positive findings. Hyperuricemia has been controlled by benzbromarone in nine patients. One patient did not take any medical treatment and died suddenly when he was 19 years old, but showed no gouty signs. Patients with Lesch-Nyhan syndrome indicated no change or aggravation of choreoathetosis or spasticity. Self-mutilation was difficult to control by any treatment with continuing effect. After the age of ten, self-mutilation declined in seven cases, and in one patient disappeared completely. Mental delay was remarkable and suspected developmental age (DA) was 7 months - four years and 10 months (chronological age, 7 years and five months - 19 years and 6 months). Mean DQ score was 15.6. Physical development was severely delayed, and weight age was 28.9-46.4%, mean 37.4% of chronological age. Future investigations will evolve clarification of CNS signs and its treatment, and etiological research of sudden death.
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PMID:Long-term follow-up of ten patients with Lesch-Nyhan syndrome. 376 72

Deficient hypoxanthine-guanine phosphoribosyl transferase (HGPRT; EC 2.4.2.8) enzymes from erythrocytes of patients with hyperuricemia and with the Lesch-Nyhan syndrome migrate 15% faster in polyacrylamide gel disc electrophoresis than the normal enzyme. A half-sister of two males with partial deficiency, who had 34% of normal HGPRT activity in her erythrocytes, yielded profiles containing two distinct zones of activity; one corresponded to the enzyme found in normal individuals and one to the variant of her half-brothers. However, in her profile her variant enzyme showed notably greater activity than that observed in her half-brothers. This increase was due to an activation of the variant by normal enzyme. Electrophoresis of mixtures of normal enzyme with partially deficient enzymes from patients with hyperuricemia and with the Lesch-Nyhan syndrome also led to activation of deficient HGPRT variants by normal enzymes. Deficient variants were also activated by normal enzyme on filtration through Sephadex G-25. Experiments in which deficient variant enzymes were activated with purified normal enzyme labeled with (125)I indicated that deficient enzymes incorporate components of the normal enzyme. No such activation of deficient enzymes was ever obtained when mixtures of deficient and normal enzymes were put together in a test tube.
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PMID:Activation of variants of hypoxanthine-guanine phosphoribosyl transferase by the normal enzyme. 434 98

We have previously described a 14-yr-old boy with hyperuricemia, renal failure, and accelerated purine production resistant in vivo and in vitro to purine analogs. This patient demonstrated normal red cell hypoxanthine-guanine phosphoribosyltransferase (HPRT) heat stability, electrophoresis at high pH, and activity at standard substrate levels. In the present report an abnormal HPRT enzyme was demonstrated by enzyme kinetic study with phosphoribosylpyrophosphate (PRPP) as the variable substrate and inhibitory studies with sodium fluoride. Apparently normal HPRT activity in a patient with hyperuricemia and gout does not exclude a functionally significant HPRT mutation.
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PMID:Hypoxanthine-guanine phosphoribosyltransferase variant associated with accelerated purine synthesis. 435 74

A family is described in which four affected males, spanning two generations, have hyperuricemia and gout accompanied by hematuria but are without severe neurologic involvement. The affected males were found to have markedly reduced levels of erythrocytic hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity; these were 5-12% with hypoxanthine and 0.5-3% with guanine as compared to controls. Erythrocytic adenine phosphoribosyltransferase (APRT) was approximately three-fold elevated in the affected individuals. The residual HGPRT activity in affected males enabled characterization of some of the properties of this mutation. The apparent Michaelis constants (km) for both hypoxanthine and guanine were essentially unchanged, whereas the km for PP-ribose-P was approximately 10-20-fold elevated for all four affected males. The enzyme was more sensitive to product inhibition by IMP and GMP than controls, and exhibited greater thermal lability at 65 degrees C than found with control lysates.
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PMID:Partial deficiency of hypoxanthine-guanine phosphoribosyltransferase with reduced affinity for PP-ribose-P in four related males with gout. 620 22

This report concerns a three month old infant who was failing to thrive. Renal insufficiency was demonstrated and attributed to aortic coarctation. However, surgical correction of the coarctation failed to correct the renal insufficiency completely and disproportionate hyperuricemia was noted. Excessive urinary excretion of uric acid was found and a moderate deficiency (6% of normal) of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) was demonstrated. When the urate over-production was corrected with allopurinol, renal function returned to normal and the child became well. The importance of over-production of urate and the resultant excessive urinary excretion of uric acid as a treatable cause of acute or persistent renal insufficiency is stressed.
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PMID:Renal failure in infancy due to over-production of urate. 659 54

Alterations in several specific enzymes have been associated with increased rates of purine synthesis de novo in human and other mammalian cells. However, these recognized abnormalities in humans account for only a few percent of the clinical cases of hyperuricemia and gout. We have examined in detail the rates of purine production de novo and purine excretion by normal and by mutant (AU-100) murine lymphoma T cells (S49) 80% deficient in adenylosuccinate synthetase [IMP:L-aspartate ligase (GDP-forming), EC 6.3.4.4]. The intracellular ATP concentration of the mutant cells is slightly diminished, but their GTP is increased 50% and their IMP, four-fold. Compared to wild-type cells, the AU-100 cells excrete into the culture medium 30- to 50-fold greater amounts of purine metabolites consisting mainly of inosine. Moreover, the AU-100 cell line overproduces total purines. In an AU-100-derived cell line, AU-TG50B, deficient in adenylosuccinate synthetase and hypoxanthine/guanine phosphoribosyltransferase (IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), purine nucleoside excretion is increased 50- to 100-fold, and de novo synthesis is even greater than that for AU-100 cells. The overexcretion of purine metabolites by the AU-100 cells seems to be due to the primary genetic deficiency of adenylosuccinate synthetase, a deficiency that requires the cell to increase intracellular IMP in an attempt to maintain ATP levels. As a consequence of elevated IMP pools, large amounts of inosine are secreted into the culture medium. We propose that a similar primary genetic defect may account for the excessive purine excretion in some patients with dominantly inherited hyperuricemia and gout.
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PMID:Purine oversecretion in cultured murine lymphoma cells deficient in adenylosuccinate synthetase: genetic model for inherited hyperuricemia and gout. 695 54

Information on a familial syndrome of hyperuricemia and renal disease with or without gout was obtained on 33 of 41 blood relatives: Nine had renal disease; abnormalities of the urinary sediments were minimal; serum uric acid levels were elevated in seven and were not measured in two. Hyperuricemia was noted in three additional family members without evidence of renal disease. Goulty arthritis (three patients) did not precede renal disease. One individual had hyperuricosuria. The following erythrocyte purine enzyme levels were normal: adenine phosphoribosyltransferase, hypoxanthine-guanine phosphoribosyltransferase, phosphoribosylpyrophosphate, synthetase, adenosine deaminiase, and purine nucleoside phosphorylase. Renal biopsy specimens showed focal global and segmental sclerosis of glomeruli, occasional hypercellularity, foci of atrophic tubules, chronic interstitial inflammation, and folding and wrinkling of glomerular basement membrane without electron-dense deposits. There were no immunofluorescent abnormalities.
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PMID:Familial hyperuricemia and renal disease. 739 93

We have sequenced and studied the expressed protein of an HPRT mutation characterized by 5-12% residual erythrocyte activity, for which affected males exhibit hyperuricemia, arthritis and renal disease but are without severe neurological involvement. The HPRTMoose Jaw mutation is due to a single C to G transversion at nucleotide 582 relative to initiation of translation corresponding to substitution of aspartate 194 by glutamate. The mutant and wild type proteins were expressed and purified using the bacterial expression vector, pMAL-c2. The Km for hypoxanthine was increased 12-fold from 0.94 +/- 0.26 to 11.5 +/- 1.3 microM for control and mutant respectively. The apparent Km for PP-ribose-P was increased 44-fold from 6.8 +/- 0.6 to 295 +/- 7 microM for control and mutant respectively. Although the kcat of the mutant protein was equivalent to wild type, the catalytic efficiency, kcat/Km, of the purified mutant protein was only 6 and 3% of wild type with hypoxanthine and PP-ribose-P respectively. The mutant protein also exhibited positive cooperativity with PP-ribose-P, having a Hill coefficient of 2.3. The decreased substrate affinities and PP-ribose-P associated cooperativity of HPRTMoose Jaw provide additional evidence for the influence of carboxy-terminal residues of HPRT in specific catalytic functions.
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PMID:Sequence, expression and characterization of HPRTMoose Jaw: a point mutation resulting in cooperativity and decreased substrate affinities. 798 18

We have identified a mutation in the gene coding for the enzyme hypoxanthine phosphoribosyltransferase in a pediatric patient with hyperuricemia and nephrolithiasis. The mutation is a nucleotide substitution causing an amino acid substitution in the hypoxanthine phosphoribosyltransferase protein. In this patient, fibroblasts but not lymphocytes showed resistance to 6-thioguanine, and reduced enzyme activity was detected in lymphocytes. These results are consistent with the intermediary phenotype associated with partial hypoxanthine phosphoribosyltransferase enzyme deficiency. Altogether, six males in this family suffered from hyperuricemic symptoms, and small differences in phenotype were seen.
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PMID:A missense mutation in the hypoxanthine phosphoribosyltransferase gene in a pediatric patient with hyperuricemia. 824 73


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