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)

Hyperuricaemia in Down's syndrome is unreleated to the activity of phosphoribosylamidotransfrease, which catalyses the activity of the first specific step on the purine biosynthetic pathway, and to the activity of hypoxanthine phosphoribosyltransferase and phosphoribosylpyrophosphate synthetase, abnormalities of which are known to be associated with hyperuricaemia. Immunological studies involving serum immunoglobulins, natural E. coli antibodies, test immunization with pneumococcal polysaccharide type III (PnPS), in vitro lymphocyte transformation to mitogens, and pokeweed mitogen (PWM) induced immunoglobulin production showed no difference between hyperuricaemic or normouricaemic Down's patients and institutionalized controls. The Down's patients had higher serum IgA, IgG and IgE, and some also produced more immunoglobulin in PWM-stimulated lymphocyte cultures when compared to normal healthy controls. However, both patients with Down's syndrome and the institutionalized controls had significantly lower responses to PnPs than normal healthy controls. The only deficiency confined to the Down's patients was a signficant depression in delayed hypersensitivity to dinitrochlorobenzene. These findings indicate that the in vivo abnormality of depressed cellular and humoral immunity in Down's patients is not paralleled by in vitro function as measured by PHA lymphocyte transformation and immunoglobulin production by PWM-stimulated lymphocytes. There is also no apparent link between a putative defect in purine metabolism in Down's patients and any immunological abnormalities.
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PMID:Immunological and purine enzyme studies on hyperuricaemic and normouricaemic patients with Down's syndrome. 15 48

The alterations of three erythrocyte purine enzymes were studied in 12 patients with diseases associated with reticulocytosis, two patients with a partial deficiency of hypoxanthine-guanine phosphoribosyltransferase, seven patients with severe megaloblastic anemia, and 14 normal subjects. The specific activity of adenine phosphoribosyltransferase was positively correlated (r = 0.81) with the reticulocyte percentate in ten patients with a normal hypoxanthine-guanine phosphoribosyltransferase. Two apparent types of alterations of this enzyme were distinguished: (1) increased specific activity with a normal half life as in megaloblastic anemia, and (2) a prolonged half life with or without an elevation of specific activity as in the deficiency of hypoxanthine-guanine phosphoribosyltransferase. Hypoxanthine-guanine phosphoribosyltransferase and phosphoribosylpyrophosphate synthetase were increased in megaloblastic anemia, but were not correlated with the reticulocyte percentage and did not have a consistent change in the half life in the other disorders studied. The data show that acquired disorders associated with reticulocytosis may cause an elevation of the specific activity of purine enzymes in peripheral circulating erythrocytes. Therefore, these factors must be carefully considered in the interpretation of an elevated level of enzyme activity.
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PMID:Acquired increases of human erythrocyte purine enzymes. 17 42

Nine independently derived clones of mutagenized rat hepatoma cells selected for resistance to 6-mercaptopurine (6-MP) or 6-thioguanine (6-ThioG) have been isolated. Each has severely reduced catalytic activity of hypoxanthine-guanine phosphoribosyltransferase (HPRT) and seven of them possess significantly increased activities of phosphoribosylpyrophosphate (PRPP) synthetase. The degrees of elevations of PRPP synthetase activities do not correlate with the degrees of deficiencies of HPRT activities. The cells from one of these clones, 1020/12, posses 40% of the normal HPRT catalytic activity and overproduce purines. We have extensively examined the cells from this clone. Immunotration studies of 1020/12 cells indicate that there is a mutation in the structural gene for HPRT. Although they possess increased specific catalytic activities of the enzyme. PRPP synthetase, the catalytic parameters, heat stability, and isoelectric pH of PRPP synthetase from 1020/12 cells are indistinguishable from those of the enzyme from wild-type cells. The cause of purine overproduction by 1020/12 cells appears to be the elevated PRPP synthetase activity, rather than a PRPP "sparing" effect stemming from reduced HPRT activity. Support for this idea is provided by the observation that the complete loss of HPRT activity in a clone derived from 1020/12 cells does not further enhance the levels of PRPP synthetase or purine overproduction. We propose that the elevated levels of PRPP synthetase activity in these HPRT deficient cells result from a mutational event in the structural gene for HPRT, and that this causes the disruption of a previously undescribed regulatory function of this gene on the expression of the PRPP synthetase gene.
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PMID:Increased PRPP synthetase activity in cultured rat hepatoma cells containing mutations in the hypoxanthine-guanine phosphoribosyltransferase gene. 17 76

In subconfluent cultures of fibroblasts from patients with complete or partial deficiencies of hypoxanthine-guanine phosphoribosyltransferase, phosphoribosylpyrophosphate synthetase activity is elevated. The abnormally high catalytic activity of the synthetase appears to account for the overproduction of purines by the cultured mutant cells and presumably for that by the patients.
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PMID:Phosphoribosylpyrophosphate synthetase is elevated in fibroblasts from patients with the Lesch-Nyhan syndrome. 18 Jun 3

Sixty-eight independent hybrid clones were isolated after irradiated normal human lymphocytes were fused with Chinese hamster fibroblasts lacking hypoxanthine-guanine phosphoribosyltransferase activity. The cells were grown under selective conditions requiring retention of the X chromosome-linked locus for human hypoxanthine-guanine phosphoribosyltransferase. The frequency and patterns of cotransference of human phosphoribosylpyrophosphate synthetase with the selected marker and with additional X-linked enzymatic markers confirm X linkage of the structural gene for human phosphoribosylpyrophosphate synthetase and support assignment of this gene to a position on the long arm of the X, between the loci for alpha-galactosidase and hypoxanthine-guanine phosphoribosyltransferase.
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PMID:Regional localization of the gene for human phosphoribosylpyrophosphate synthetase on the X chromosome. 21 84

Human peripheral blood leukocytes were studied for the presence and the regulatory properties of the pathway of de novo synthesis of purine nucleotides. The cells were found to incorporate the labeled precursors formate and glycine into purines. The rate of [14C]-formate incorporation was decreased by several compounds known to inhibit purine synthesis by affecting the activity by glutamine phosphoribosylpyrophosphate (PRPP) amidotransferase, the first committed enzyme in the pathway, either through decreasing the availability of PRPP, a substrate for this enzyme, or through exerting inhibition on this enzyme. PRPP availability in the leukocyte was found to be limiting for purine synthesis. Increased PRPP availability resulting from activation of PRPP synthetase by increasing inorganic phosphate (Pi) concentration caused acceleration of purine synthesis. On the other hand, no clear-cut evidence was obtained for the availability of ribose-5-phosphate in the leukocyte being rate limiting at physiological extracellular Pi concentration for PRPP generation, and thus for purine synthesis. However, the addition of methylene blue, which accelerates the oxidative pentose shunt that produces ribose-5-phosphate, resulted in acceleration of PRPP generation and of purine synthesis only when PRPP synthetase was largely activated at high Pi concentration. These results may be taken to suggest that ribose-5-phosphate availability is indeed not limiting for PRPP generation under physiological conditions. Purine synthesis de novo was accelerated more than 13-fold in the leukocytes of two gouty patients affected with partial deficiency of hypoxanthine-guanine phosphoribosyltransferase, but was normal in the leukocytes of an obligate heterozygote for this enzyme abnormality. The results domonstrate in peripheral human leukocytes the presence of the complete pathway of de novo synthesis of purine nucleotides and the manifestation in these cells of the biochemical consequences of hypoxanthine-guanine phosphoribosyltransferase deficiency, i.e., increased availability of PRPP and acceleration of purine synthesis de novo. The results indicate the usefulness of leukocytes as a model tissue for the study of purine metabolism in man.
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PMID:De novo synthesis of purine nucleotides in human peripheral blood leukocytes. Excessive activity of the pathway in hypoxanthine-guanine phosphoribosyltransferase deficiency. 95 68

Six generations of a Japanese family had gouty arthritis and progressive nephropathy. Data on nine of 51 women (18%) and 15 of 66 men (23%) with either asymptomatic hyperuricaemia, gouty arthritis, or renal insufficiency were obtained. Renal function in four men and one woman with hyperuricaemia or gouty arthritis was also examined. Urinary excretion of uric acid was decreased in all subjects examined, including the young. Erythrocyte phosphoribosylpyrophosphate synthetase and hypoxanthine-guanine phosphoribosyltransferase activities determined in 10 patients were normal. Some patients had been treated with allopurinol to reduce serum uric acid concentrations, but the treatment did not prevent progression of renal impairment. Transmission of the disease in this large family is considered to be autosomal dominant. The data suggest that the disease in this family is the same entity as that described by other workers--that is, familial urate nephropathy. As far as is known this is the largest family with this disease so far reported.
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PMID:Autosomal dominant transmission of gouty arthritis with renal disease in a large Japanese family. 184 94

Cloned cDNAs representing the entire, homologous (80%) translated sequences of human phosphoribosylpyrophosphate synthetase (PRS) 1 and PRS 2 cDNAs were utilized as probes to localize the corresponding human PRPS1 and PRPS2 genes, previously reported to be X chromosome linked. PRPS1 and PRPS2 loci mapped to the intervals Xq22-q24 and Xp22.2-p22.3, respectively, using a combination of in situ chromosomal hybridization and human x rodent somatic cell panel genomic DNA hybridization analyses. A PRPS1-related gene or pseudogene (PRPS1L2) was also identified using in situ chromosomal hybridization at 9q33-q34. Human HPRT and PRPS1 loci are not closely linked. Despite marked cDNA and deduced amino acid sequence homology, human PRS 1 and PRS 2 isoforms are encoded by genes widely separated on the X chromosome.
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PMID:Cloning of cDNAs for human phosphoribosylpyrophosphate synthetases 1 and 2 and X chromosome localization of PRPS1 and PRPS2 genes. 196 53

1. The synthesis of nicotinamide-adenine dinucleotide from nicotinamide and nicotinic acid was compared over different time scales at both physiological (0.7 mumol/l) and high (0.2-3 mmol/l) substrate concentrations in erythrocytes from three patients with hypoxanthine-guanine phosphoribosyltransferase (hypoxanthine phosphoribosyltransferase, EC 2.4.2.8) deficiency (including one Lesch-Nyhan patient) and from one patient with phosphoribosylpyrophosphate synthetase superactivity. The above disorders are associated with grossly altered erythrocyte nicotinamide-adenine dinucleotide levels. 2. At the physiological substrate concentration and incubation times up to 2 h, nicotinamide proved the most efficient nicotinamide-adenine dinucleotide precursor for erythrocytes from both patients and control subjects. The conversion of nicotinamide to its mononucleotide, but not further metabolism, was impaired in phosphoribosylpyrophosphate synthetase-mutant cells. The Lesch-Nyhan and phosphoribosylpyrophosphate synthetase-mutant cells were unusual in that both showed no further stimulation of nucleotide synthesis at 18 mmol/l Pi compared with 1 mmol/l. 3. At the high substrate concentrations, using 18 mmol/l Pi, nicotinamide was a poor precursor in all instances. Using nicotinic acid, nucleotide formation was 30-fold that from nicotinamide, reaching its maximum at 0.2 mmol/l. Conversion of nicotinic acid to nicotinamide-adenine dinucleotide in the phosphoribosylpyrophosphate synthetase-mutant cells was again grossly impaired. 4. There was no evidence for increased nicotinamide-adenine dinucleotide breakdown in the phosphoribosylpyrophosphate synthetase-mutant cells under any of the above conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regulation of nicotinamide-adenine dinucleotide synthesis in erythrocytes of patients with hypoxanthine-guanine phosphoribosyltransferase deficiency and a patient with phosphoribosylpyrophosphate synthetase superactivity. 215 55

Deficiency of uridine-5'-monophosphate (UMP) synthase in dairy cattle, a condition analogous to human hereditary orotic aciduria, is reviewed with consideration of similarities and differences between the enzyme deficiency in humans and cattle. New findings regarding the bovine condition are reported including presence of the enzyme deficiency in numerous tissues and absence of substantial effects on other aspects of nucleotide metabolism. Specifically, erythrocyte concentration of phosphoribosylpyrophosphate (PRPP) and activities of PRPP synthetase, adenine phosphoribosyltransferase, and hypoxanthine-guanine phosphoribosyltransferase appear to be normal in cattle heterozygous for UMP synthase deficiency.
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PMID:Deficiency of UMP synthase in dairy cattle: a model for hereditary orotic aciduria. 244 44


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