Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human erythrocyte lysate proteins were resolved into over 250 discrete spots by two-dimensional electrophoresis using isoelectric focusing in the first dimension and electrophoresis in the presence of sodium dodecyl sulfate, (SDS) in the second. The overwhelming excess of hemoglobin has made such analyses difficult in the past. However, with the ISO-DALT two-dimensional electrophoresis system, large numbers of red cell proteins can be mapped in the presence of hemoglobin. When hemoglobin and several other major proteins are removed by adsorption to DEAE-cellulose, additional minor components are seen, giving a total of over 275. With the use of purified preparations, the map positions of five cell enzymes or their subunits were determined: pyruvate kinase, catalase, glucose-6-phosphate dehydrogenase, hypoxanthine phosphoribosyltransferase, and carbonic anhydrase. The mapping techniques described complement and extend those traditionally used to find human red cell protein variants.
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PMID:Red cell proteins. I. Two-dimensional mapping of human erythrocyte lysate proteins. 10 31

In a patient with paroxysmal nocturnal haemoglobinuria (PNH) enzymatic activities of erythrocytes and leucocytes were studied. Studies of autohaemolysis were also performed. The following erythrocytary enzymes were measured: Glucose-6-phosphate dehydrogenase (G-6-PD), pyruvate kinase (PK), glutathione reductase (GR), and acetylcholinesterase (AcChE). The following enzymes were measured in leucocytes: Adenosine deaminase, purine nucleoside phosphorylase, adenine phosphoribosyltransferase, hypoxanthine phosphoribosyltransferase and adenosine kinase. Normal activity of G-6-PD, GR and PK in erythrocytes was found. In leucocytes and lymphocytes activity of purine nucleoside phosphorylase was reduced. Auto-haemolysis in vitro was increased, which could not be compensated by addition of glucose or ATP.
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PMID:Erythrocyte and leucocyte enzymes in a case of paroxysmal nocturnal haemoglobinuria. 10 10

We have studied somatic cell hybrids between P3x63Ag8 mouse myeloma cells deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) and either human peripheral lymphocytes or human lymphoblastoid or myeloma cells for the production of human immunoglobulin chains and for the expression of enzyme markers assigned to each of the different human chromosomes. Human chromosome 14 was the only human chromosome present in all independent hybrids producing mu, gamma, and alpha human heavy chains. In two of the independent hybrids that produced human heavy chains, human chromosome 14 was the only human chromosome present in the hybrid cells. Loss of human chromosome 14 from these hybrids resulted in the concomitant loss of their ability to produce human immunoglobulin heavy chains. In view of these results, we conclude that the genes for human immunoglobulin heavy chains are located on human chromosome 14 in immunoglobulin-producing human cells.
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PMID:Chromosomal location of the genes for human immunoglobulin heavy chains. 11 99

Hypoxanthine uptake and hypoxanthine phosphoribosyltransferase activity (EC 2.4.2.8) were determined in germinated conidia from the adenine auxotrophic strains ad-1 and ad-8 and the double mutant strain ad-1 ad-8. The mutant strain ad-1 appears to lack aminoimidazolecarboximide ribonucleotide formyltransferase (EC 2.1.2.3) or inosine 5'monophosphate cyclohydrolase (EC 3.5.1.10) activities, or both, whereas the ad-8 strain lacks adenylosuccinate synthase activity (EC 6.3.4.4). Normal (or wild-type) hypoxanthine transport capacity was found to the ad-1 conidia, whereas the ad-8 strains failed to take up any hypoxanthine. The double mutant strains showed intermediate transport capacities. Similar results were obtained for hypoxanthine phosphoribosyl-transferase activity assayed in germinated conidia. The ad-1 strain showed greatest activity, the ad-8 strain showed the least activity, and the double mutant strain showed intermediate activity levels. Ion-exchange chromatography of the growth media revealed that in the presence of NH+/4, the ad-8 strain excreted hypoxanthine or inosine, the ad-1 strain did not excrete any purines, and the ad-1 ad-8 double mutant strain excreted uric acid. In the absence of NH+/4, none of the strains excreted any detectable purine compounds.
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PMID:Regulation of hypoxanthine transport in Neurospora crassa. 13 58

Somatic mutation and neoplastic transformation of diploid Syrian hamster embryo cells were examined concomitantly. Mutations induced by benzo[a]pyrene and N-methyl-N'-nitro-N-nitrosoguanidine were quantitated at the hypoxanthine phosphoribosyltransferase and Na(+)/K(+) ATPase loci and compared to phenotypic transformations measured by changes in cellular morphology and colony formation in agar. Both cellular transformations had characteristics distinct from the somatic mutations observed at the two loci. Morphological transformation was observed after a time comparable to that of somatic mutation but at a frequency that was 25- to 540-fold higher. Transformants capable of colony formation in agar were detected at a frequency of 10(-5)-10(-6), but not until 32-75 population doublings after carcinogen treatment. Although this frequency of transformation is comparable to that of somatic mutation, the detection time required is much longer than the optimal expression time of conventionally studied somatic mutations. Neoplastic transformation of hamster embryo cells has been described as a multistep, progressive process. Various phenotypic transformations of cells after carcinogen treatment may represent different stages in this progressive transformation. The results are discussed in this context and the role of mutagenesis in the transition between various stages is considered. Neoplastic transformation may be initiated by a mutational change, but it cannot be described completely by a single gene mutational event involving a dominant, codominant, or X-linked recessive locus. Neoplastic transformation induced by chemical carcinogens is more complex than a single gene mutational process. Thus, this comparative study does not give experimental support to predictions of the carcinogenic potential of chemicals based on a simple extrapolation of the results obtained from conventional somatic mutation assays.
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PMID:Relationship between somatic mutation and neoplastic transformation. 15 Jun

6-Methylpurine, an analog of adenine, inhibits the growth of Neurospora crassa. From kinetic studies it was found that 6-methylpurine is converted to its nucleotide form by adenine phosphoribosyltransferase (EC 2.4.2.7), and inhibits the de novo purine biosynthesis. Adenine relieves the growth inhibition caused by 6-methylpurine, whereas hypoxanthine is not very effective. Studies dealing with hypoxanthine utilization in the presence of 6-methylpurine indicated a severely reduced uptake of hypoxanthine and a general slowdown in its further metabolism. Two mutants (Mepr-3 and Mepr-10) which are resistant to 6-methylpurine were characterized. Studies of purine base uptake and the in vivo and in vitro conversion to nucleotides indicated that Mepr-10 may be an adenine phosphoribosyltransferase-defective mutant, whereas Mepr-3 may be a mutant with altered feedback response to 6-methylpurine. Both mutants showed a severely lowered hypoxanthine phosphoribosyltransferase activity, but because 6-methylpurine did not have any effect on the conversion of hypoxanthine to IMP in the wild type, it was concluded that 6-methylpurine resistance in these mutants cannot be due to lowered hypoxanthine phosphoribosyltransferase activity, but rather that the lowering of enzyme activity may be a secondary effect.
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PMID:Nature of 6-methylpurine inhibition and characterization of two 6-methylpurine-resistant mutants of Neurospora crassa. 15 98

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

Hypoxanthine phosphoribosyltransferase (EC 2.4.2.8) from rat brain or human erytherocytes can be irreversibly inactivated by incubation with periodate-oxidized analogues of the enzyme products GMP or IMP. This inhibition is specific and directed against the product binding site of the enzyme. Inactivation is not produced by periodate-oxidized AMP or other aldehydes, for example periodate-oxidized glycerol. The inactivation is concomitant with the binding of the inhibitor to the enzyme protein. The bound inhibitor cannot be removed from the protein by dialysis, Sephadex chromatography or polyacrylamide-gel electrophoresis. Adenine phosphoribosyltransferase (EC 2.4.2.7), on the other hand, is not influenced by any of the inhibitors mentioned above.
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PMID:Irreversible inactivation of hypoxanthine phosphoribosyltransferase by periodate oxidized nucleotides. 16 42

Adenine, guanine, and hypoxanthine were rapidly incorporated into the acid-soluble nucleotide pool and nucleic acids by wild type Novikoff cells. Incorporation followed normal Michaelis-Menten kinetics, but the following evidence indicates that specific transport processes precede the phosphoribosyltransferase reactions and are the rate-limiting step in purine incorporation by whole cells. Cells of an azaguanine-resistant subline of Novikoff cells which lacked hypoxanthine-guanine phosphoribosyltransferase activity and failed to incorporate guanine or hypoxanthine into the nucleotide pool, exhibited uptake of guanine and hypoxanthine by a saturable process. Similarly, wild type cells which had been preincubated in a glucose-free basal medium containing KCN and iodoacetate transported guanine and hypoxanthine normally, although a conversion of these purines to nucleotides did not occur in these cells. The mutant and KCN-iodoacetate treated wild type cells also exhibited countertransport of guanine and hypoxanthine when preloaded with various purines, uracil, and pyrimidine nucleosides. The cells also possess a saturable transport system for uracil although they lack phosphoribosyltransferase activity for uracil. In the absence of phosphoribosylation, none of the substrates was accumulated against a concentration gradient. Thus transport is by facilitated diffusion (nonconcentrative transport). Furthermore, the apparent Km values for purine uptake by untreated wild type and azaguanine-resistant cells were higher and the apparent Vmax values were lower than those for the corresponding phosphoribosyltransferases...
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PMID:Purine and pyrimidine transport by cultured Novikoff cells. Specificities and mechanism of transport and relationship to phosphoribosylation. 16 3

Somatic cell hybrid clones between either C57BL/6 or Balb/c mouse peritoneal macrophages and two different simian virus 40 (SV40)-transformed human cell lines deficient in hypoxanthine phosphoribosyltransferase (EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase) were obtained in hypoxanthine-aminopterin-thymidine selective medium. All the hybrid cell clones contained the human chromosome 7, which carries the SV40 genome, and were SV40 tumor (T)-antigen positive. No hybrid cell clones studied displayed the density-dependent inhibition of cell growth characteristic of normal cells; all clones had a high saturation density and gave origin to cell colonies when plated in soft agar. Since the expression of the transformed phenotype was always associated with the presence of the human chromosome 7, which carries the SV40 genome, it is concluded that this chromosome contains gene(s) [Tr gene(s)] coding for "transforming factor(s)."
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PMID:Assignment of gene(s) for cell transformation to human chromosome 7 carrying the simian virus 40 genome. 16 24


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