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)

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

A new fluorimetric method to assay HGPRT (hypoxanthine-guanine phosphoribosyl transferase, EC 2.4.2.8) from human red cell lysates using 6MP (6-mercaptopurine) as substrate is described. This assay is compared with an existing spectrophotometric method using hypoxanthine as substrate. Precision, sensitivity limits and kinetic differences of these assays are reported.
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PMID:A fluorimetric assay of the phosphoribosylation of 6-mercaptopurine in human blood cells. 4 Jul 20

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 development of our knowledge of the immune system has been reviewed and evidence presented of the need for a rapid rate of purine synthesis de novo for the proliferative events in this process. The mechanism of the inhibition of the immune system in a model of ADA deficiency has been studied intensively and considerable indirect evidence obtained of adenosine toxicity as a possible mediator of a reversible inhibition of proliferation of T-cells and to a slightly lesser extent B-cells. A secondary inhibition of ADA by inosine accumulation in PNP deficiency is proposed as a unifying hypothesis in which a somewhat lesser adenosine toxicity would inhibit proliferation only only of T-cells. The correction of the immune response by addition of ADA both in vitro and in vivo provides strong evidence in favor of this view. In HPRT deficiency no evidence was found of a gross impairment of the immune system; however, the HPRT enzyme is required for inhibition of the immune response by 6MP in a variety of systems using different mitogenic stimuli.
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PMID:Immunological aspects of purine metabolism. 19 75

The adenylate kinase 1 (AK1), adenylate kinase3 (AK3), and aconitaseS (ACONS) genes have been assigned to chromosome 9 in man by employing an X/9 translocation segregating in man-mouse somatic cell hybrids. Segregation was controlled by taking advantage of the HAT/8-azaguanine selection-counterselection strategy directed at the X-linked HPRT locus. Assignment of AK1 to chromosome 9 has suggested the assignment of the ABO blood-group locus and the nail-patella (Np) locus to 9, since both loci are linked to AK1 by family studies.
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PMID:Mapping AK1, ACONs, and AK3 to chromosome 9 in man employing and X/9 translocation and somatic cell hybrids. 19 13

Chinese hamster X mouse somatic cell hybrids segregating mouse chromosomes were examined for their mouse chromosome content using trypsin-Giemsa (GTG) banding and Hoechst 33258 staining techniques. Simultaneously, they were scored for the presence of 24 mouse enzymes. The results confirm the assignments of 11 genes previously mapped by sexual genetics: Dip-1 and Id-1 to chromosome 1; Pgm-2 and Pgd to 4; Pgm-1 to 5; Gpi-1 to 7; Gr-1 to 8; Mpi-1 and Mod-1 to 9; Np-1 and Es-10 to 14. They also confirm chromosomally the assignments of 3 genes that were made by other somatic cell genetic studies: Aprt to 8; Hprt and alpha-gal to the X chromosome. But most importantly, four enzyme loci are assigned to four chromosomes that until now were not known to carry a biochemical marker which is expressed in cultured cells: Trip-1 to 10; Dip-2 to 18; Acp-1 to 12; and Ak-1 to 2. Cytogenetic examination of clones showing discordant segregation of HPRT and A-GAL, suggested the assignment of alpha-gal to region XE leads to XF of the mouse X chromosome. The cytologic studies provide a comparison between data from sexual genetics and somatic cell hybrids and validate hybrid cell techniques. They provide evidence of the reliability of scoring chromosomes by GTG and Hoechst staining and stress the importance of identifying clones with multiple chromosome rearrangements. Striking examples of norandom segregation of mouse chromosomes were observed in these hybrids with preferential retention of 15 and segregation of 11 and the Y chromosome.
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PMID:Gene mapping in Mus musculus by interspecific cell hybridization: assignment of the genes for tripeptidase-1 to chromosome 10, dipeptidase-2 to chromosome 18, acid phosphatase-1 to chromosome 12, and adenylate kinase-1 to chromosome 2. 19 84

Evidence is presented for the assignment of the gene for adenosine kinase to Mus musculus chromosome 14 by synteny testing and karyotypic analysis of mouse X Chinese hamster somatic cell hybrid clones. ADOK and two enzymes previously mapped to mouse chromosome 14, NP and ES-10, were expressed concordantly in 29 hybrid clones. Chromosome analysis confirmed this assignment. Syntenic evidence is also presented using several clones of a gene transfer system in which the gene for human HPRT had integrated into modified mouse chromosome 14's.
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PMID:Assignment of the gene for adenosine kinase to chromosome 14 in Mus musculus by somatic cell hybridization. 20 12

Polyethylene glycol-1000 (PEG-1000) induced fusion of HPRT (E.C. 2.4.2.8) deficient Chinese hamster cells with alpha-galactosidase A (E.C. 2.3.1.22) deficient cells from a patient with Fabry's disease yielded hybrids which contained both human and hamster HPRT, G6PD (E.C. 1.1.1.49), and APRT (E.C. 2.4.2.7) and Chinese hamster alpha-galactosidase B. Thus PEG-1000 mediated somatic cell fusion led to reexpression of Chinese hamster HPRT. It did not restore the expression of human alpha-galactosidase. Since PEG-1000 treatment of HPRT- Chinese hamster cells in the absence of human cells yielded no HPRT+ cells, it is concluded that the element responsible for the restoration of rodent HPRT was contributed by the human cells and not by the agent employed to promote fusion.
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PMID:Reexpression of HPRT activity following cell fusion with polyethylene glycol. 20 82

We have used trypsin-Wright's banding ("GTG-banding") to analyze the chromosome content in two sublines of the SV40-transformed human cell line LNSV, derived from fibroblasts of a patient with HPRT deficiency. Both LNSV sublines (GM-847 and "LNSV") were heteroploid and showed considerable numerical and structural chromosome variability. Nineteen rearranged chromosomes which were observed at high frequency have been set aside as "marker chromosomes," and their probable derivation from normal human chromosomes has been described in PARIS CONFERENCE (1971) nomenclature. Heterogeneity within these uncloned sublines appears to increase with time in culture, and no evidence was found for evolution of a karyotypically stable cell population. The results are of general significance for cell genetic studies using established cell lines.
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PMID:Karyotype evolution of the simian virus 40--transformed human cell line LNSV. 21 30

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


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