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)

Five clones of mouse neuroblastoma cells able to grow in hypoxanthine-aminopterin-thymidine containing medium were isolated from a hypoxanthine-guanine phosphoribosyltransferase (HGPRT; EC 2.4.2.8; IMP: pyrophosphate phosphoribosyltransferase) deficient cell line. These hypoxanthine-aminopterin-thymidine resistant revertant clone had 45-55% of wild-type cell HGPRT activity. Kinetic studies indicated that the HGPRT in revertant clones had a reduced maximal velocity as compared to wild type cells based on cell protein. Apparent Km values of HGPRT for hypoxanthine and 5-phosphoribosyl-1-pyrophosphate were similar in wild-type and revertant cells. Heat inactivation studies demonstrated a similar heat lability for HGPRT in revertant and wild-type cells. An antibody fraction prepared from serum of rabbits immunized with HGPRT partially purified from mouse liver was used to measure the amount of cross-reacting material in normal and revertant clones. The revertant clones had one-half the amounth of cross-reacting material present in wild-type cells, based on a given amount of cell protein. These data indicate that the revertant cells may contain fewer HGPRT molecules with unaltered catalytic activity.
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PMID:Reversion in expression of hypoxanthine-guanine phosphoribosyltransferase in 6-thioguanine resistant neuroblastoma: evidence for reduced enzyme levels associated with unaltered catalytic activity. 1 84

The spot corresponding to hypoxanthine phosphoribosyltransferase (HPRT; IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) has been identified in two-dimensional polyacrylamide gels of HeLa cell extracts. This spot is absent in gels of 24 HPRT dificient mutants. A missense mutant displays a new HPRT spot at the same molecular weight but different isoelectric focusing position. Five independently isolated revertants of the missense mutant display spots corresponding to both the wild-type and mutant proteins indicating that they synthesize HPRT from two separate genes. If the missense protein is synthesized from a mutated form of the initially active HPRT gene, then wild-type HPRT protein in the revertants must be snythesized from a newly activated but prevously silent wild-type gene. The newly activated gene in the revertants of the missense mutation appears unstable producing a high frequency of spontaneous HPRT mutants.
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PMID:Analysis of HeLa cell hypoxanthine phosphoribosyltransferase mutants and revertants by two-dimensional polyacrylamide gel electrophoresis: evidence for silent gene activation. 6 48

The possible factors in the pathogenesis of the brain damage and megaloblastic anaemia in the Lesch-Nyhan syndrome are discussed. Disordered growth and function appear to be limited to the brain, bone marrow and general body stature, yet the purine salvage enzyme hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8, HGPRT), although present in variable amounts in different tissues, is ubiquitous, a fact which suggests that other factors than HGPRT deficiency alone determine the pattern of tissue damage. Recent evidence suggests that the specific tissue damage in the Lesch-Nyhan syndrome is due to lack of NGPRT in tissues with relatively reduced purine de novo capability and a greater dependence on purine salvage pathways at certain stages in their development for their supply of purine ribonucleotides. This evidence is presented together with possible mitigating factors operating in the bone marrow.
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PMID:Factors in the pathogenesis of the brain damage and anaemia in the Lesch-Nyhan syndrome. 24 94

Hypoxanthine phosphoribosyltransferase (HPRT, IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8) can be purified 5-to 10,000-fold from extracts of HeLa (human) cells by a three-step procedure consisting of high-speed centrifugation, adsorption to Sepharose-conjugated HPRT antibody, and sodium dodecyl sulfate/polyacrylamide gel electrophoresis. Purified enzyme labeled in vivo with radioactive lysine, arginine, or methionine was digested with trypsin and the tryptic peptides were separated by column chromatography on Bio-Rad cation exchanger Aminex A-5. Less than 50 ng (2 pmol) of HPRT is required to produce a tryptic peptide pattern. A methionine-labeled peptide was identified as the COOH-terminus because it was not labeled with either lysine or arginine. We have compared the tryptic peptide patterns of normal HeLaHPRT and a crossreacting HPRT protein lacking enzyme activity from HeLa mutant H23 [Milman et al. (1976) Proc. Natl. Acad. Sci. USA 73, 4589--4593]. The mutant protein has a new lysine-labeled peptide, but the chromatography patterns of arginine- or methionine-labeled peptides appear identical to those of the normal protein. The appearance in the H23 mutant HPRT protein of a new tryptic peptide provides strong evidence for a mutation in the HPRT structural gene. The tryptic peptide patterns were used to determine the total number of residues of labeled amino acid in the protein, and the values are reasonably consistent with those determined by conventional amino acid analysis pf erythrocyte HPRT.
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PMID:Tryptic peptide analysis of normal and mutant forms of hypoxanthine phosphoribosyltransferase from HeLa cells. 26 86

Mutagenized stem cells of a cultured mouse teratocarcinoma cell line were selected for resistance to the purine base analog 6-thioguanine. Cells of a resistant clone were completely deficient in activity of the enzyme hypoxanthine phosphoribosyltransferase (HPRT, IMP:pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), the same X-linked lesion as occurs in human Lesch-Nyhan disease. After microinjection into blastocysts of another genetic strain, the previously malignant cells successfully participated in normal embryogenesis and tumor-free, viable mosaic mice were obtained. Cells of tumor lineage were identified by strain markers in virtually all tissues of some individuals. Mature function of those cells was evident from their tissue-specific products (e.g., melanins, liver proteins). These mutagenized teratocarcinoma cells are therefore developmentally totipotent. Retention of the severe HPRT deficiency in the differentiated state was documented in extracts of mosaic tissues by depressed specific activity of the enzyme, and also by presence of unlabeled clones in autoradiographs of explanted cells incubated in [(3)H]hypoxanthine. Some mosaic individuals had mutant-strain cells in only one or a few tissues. Such animals may provide unique opportunities to identify the tissue sources of particular aspects of the complex disease syndrome. The tissue distribution of HPRT-deficient cells suggests that selection against them is particularly strong in blood of the mosaic mice, as is already known to be the case in human heterozygotes. This phenotypic parallelism supports the expectation that afflicted F(1) male mice that might be obtained from mutant germ cells can serve as a model of the human disease.
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PMID:Mosaic mice with teratocarcinoma-derived mutant cells deficient in hypoxanthine phosphoribosyltransferase. 27 82

In the search for homologous chromosome regions in man and mouse, the locus for cytoplasmic superoxide dismutase (SOD-1; superoxide:superoxide oxidoreductase, EC 1.15.1.1) is of particular interest. In man, the SOD-1 gene occupies the same subregion of chromosome 21 that causes Down syndrome when present in triplicate. Although not obviously implicated in the pathogenesis, SOD-1 is considered to be a biochemical marker for this aneuploid condition. Using a set of 29 mouse-Chinese hamster somatic cell hybrids, we assign Sod-1 to mouse chromosome 16. Isoelectric focusing permits distinction between mouse and Chinese hamster isozymes, and trypsin/Giemsa banding distinguishes mouse from Chinese hamster chromosomes. The mouse fibroblasts used were derived from a male mouse carrying Searle's T(X;16)16H reciprocal translocation in which chromosomes X and 16 have exchanged parts. Analysis of informative hybrids leads to regional assignment of Sod-1 to the distal half of mouse chromosome 16 (16B4 --> ter). Because the Chinese hamster cell line (380) used for cell hybridization is deficient in hypoxanthine phosphoribosyltransferase (HPRT; IMP: pyrophosphate phosphoribosyltransferase, EC 2.4.2.8), that part of the mouse X chromosome carrying the complementing Hprt gene can be identified by selection in hypoxanthine/aminopterin/thymidine medium and counterselection in 8-azaguanine. Mouse Hprt is on the X(T) translocation product containing the proximal region X cen --> XD.
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PMID:Assignment of the gene for cytoplasmic superoxide dismutase (Sod-1) to a region of chromosome 16 and of Hprt to a region of the X chromosome in the mouse. 29 39

The purine phosphoribosyltransferases have emerged as important enzymes in the metabolic economy of the developing human. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT, EC 2.4.2.8) catalyses the conversion of hypoxanthine and guinine into their respective nucleotides. Inherited variation in HGPRT first became evident through clinical observations with the definition of the Lesch-Nyhan syndrome. In this disorder, HGPRT activity in erythrocytes is almost zero, although the fact that sensitive electrophoretic analysis reveals a tiny amount of activity suggests that a protein of altered structure is present. Furthermore, this variant enzyme has been activated by manipulation in the presence of small amounts of normal enzyme. Nevertheless, no cross-reacting material could be detected in lysates of red cells or fibroblasts of patients with the syndrome when tested with antiserum prepared in rabbits to normal erythrocyte HGPRT. We have tested for the presence of cross-reacting material in 18 patients, and all were negative. More HGPRT variants are coming to light. Most of the patients have renal stone disease or gout but no other feature of the Lesch-Nyhan syndrome. In one family four affected males displayed about 5% of normal activity, and the enzyme migrated electrophoretically more rapidly than normal. Cross-reacting material could not be demonstrated in erythrocyte lysates, although it was clear that a variant protein was present. A boy with renal stone disease has been found to have about 1% of normal erythrocyte activity of HGPRT. Cross-reacting material was found in his erythrocytes. The data indicate that mutations which produce diminished enzyme activity in this protein with a distinct subunit structure may or may not so alter the tertiary state of the protein that immunoreactive sites are no longer available to antibody prepared against the normal enzyme. So far whenever a variant normal HGPRT has been found there has been an identifiable clinical illness. The different forms of illness provide for correlation of molecular structure and function in man.
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PMID:Genetic heterogeneity at the locus for hypoxanthine-guanine phosphoribosyltransferase. 30 34

Procedures for assaying the rate of purine de novo synthesis in cultured fibroblast cells have been compared. These were (i) the incorporation of [(14)C]-glycine or [(14)C]formate in alpha-N-formylglycinamide ribonucleotide (an intermediate in the purine synthetic pathway) and (ii) the incorporation of [(14)C]-formate into newly synthesised cellular purines and purines excreted by the cell into the medium. Fibroblast cells, derived from patients with a deficiency of hypoxanthine phosphoribosyltransferase (HPRT-) (EC 2.4.2.8) and increased rates of purine de novo synthesis, were compared with fibroblasts from healthy subjects (HPRT+). Fetal calf serum, which was used to supplement the assay and cell growth medium, was found to contain sufficient quantities of the purine base hypoxanthine to inhibit purine de novo synthesis in HPRT+ cells. This inhibition was the basis of differentiation between HPRT- and HPRT+ cells. In the absence of added purine base, both cell types had similar capacities for purine de novo synthesis. This result contrasts with the increased rates of purine de novo synthesis reported for a number of human HPRT- cells in culture but conforms recent studies made on human HPRT- lymphoblast cells. The intracellular concentration and utilisation of 5-phosphoribosyl-1-pyrophosphate (P-Rib-PP), a substrate and potential controlling factor for purine de novo synthesis, were determined in HPRT- and HPRT+ cells. The rate of utilisation of P-Rib-PP in the salvage of free purine bases was far greater than that in purine de novo synthesis. Although HPRT- cells had a 3-fold increase in P-Rib-PP content, the rate of P-Rib-PP generation was similar to HPRT+ cells. Thus, in fibroblasts, the concentration of P-Rib-PP appears to be critical in the control of de novo purine synthesis and its preferential utilisation in the HPRT reaction limits its availability for purine de novo synthesis. In vivo, HPRT+ cells, in contrast to HPRT- cells, may be operating purine de novo synthesis at a reduced rate because of their ability to reutilise hypoxanthine.
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PMID:Regulation of purine de novo synthesis in cultured human fibroblasts: the role of P-ribose-PP. 43 98

The pattern of segregation of hypoxanthine phosphoribosyltransferase (HPRT, E.C. 2.4.2.8) was determined in synchronized Chinese hamster-chick red blood cell hybrids. Three hybrid lines were synchronized at the G1-S boundary. Bromodeoxyuridine pulses were subsequently applied throughout the S phase, and the frequency of the segregant clones was determined. It was found that the segregation of the chicken-specific HPRT phenotype associated with the loss of a chromosome was potentiated by bromodeoxyuridine administered during the first hour following release of the block.
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PMID:Pattern of segregation of chicken HPRT phenotype in Chinese hamster-chick red blood cell hybrids. 47 10

The patient, H.Chr.B., was among the first reported with hyperuricemia and central nervous system symptoms. He has been found to have a variant of hypoxanthine guanine phosphoribosyl transferase (HPRT; E.C.2.4.2.8) distinct from the enzyme present in patients with the Lesch-Nyhan syndrome. The patient had chroeoathetosis, spasticity, dysarthric speech, and hyperuricemia. However, his intelligence was normal and he had no evidence of self-mutilation. There was no activity of HPRT in the lysates of erythrocytes and cultured fibroblasts when analyzed in the usual manner. Using a newly developed method for the study of purine metabolism in intact cultured cells, this patient was found to metabolize some 9% of 8-14C-hypoxanthine, and 90% of the isotope utilized was converted to adenine and guanine nucleotides. In contrast, cells from patients with the Lesch-Nyhan syndrome were virtually completely unable to convert hypoxanthine to nucleotides. The patient's fibroblasts were even more efficient in the metabolism of 8-14C-guanine, which was utilized to the extent of 27%, over 80% of which was converted to guanine and adenine nucleotides. The growth of the cultured fibroblasts of this patient was intermediate in media containing hypoxanthine aminopterin thymidine (HAT), whereas the growth of Lesch-Nyhan cells was inhibited and normal cells grew normally. Similarly in 8-azaguanine, 6-thioguanine, and 8-azahypoxanthine, the growth of the patient's cells was intermediate between normal and Lesch-Nyhan cells. These observations provide further evidence for genetic heterogeneity among patients with disorders in purine metabolism involving the HPRT gene. They document that this famous patient did not have the Lesch-Nyhan syndrome.
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PMID:Utilization of purines by an HPRT variant in an intelligent, nonmutilative patient with features of the Lesch-Nyhan syndrome. 52 96


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