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)

Hypoxanthine phosphoribosyltransferase (IMP:pryophosphate phosphoribosyltransferase, EC 2.4.2.8) from human erythrocytes has been purified 13 000-fold to apparent homogeneity. The native enzyme has a sedimentation coefficient of 5.9 S, determined by analytical ultracentrifugation, and a molecular weight of 81 000-83 000, determined by sedimentation equilibrium centrifugation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicates a subunit molecular weight of 26 000, suggesting that the enzyme is a trimer. Isoelectric focusing resolves three peaks of enzyme activity at pH 5.6, 5.7 and 5.9. The amino acid composition of hypoxanthine phosphoribosyltrasferase is 17 Lys, 5 His, 12 Arg, 0 Trp, 31 Asx, 12 Thr, 14 Ser, 16 Glx, 14 Pro, 19 Gly, 12 Ala, 5 Cys, 18 Val, 5 Met, 11 Ile, 20 Leu, 10 Tyr, and 9 Phe. The enzyme appears to have a blocked N terminus.
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PMID:Human hypoxanthine phosphoribosyltransferase. Purification and properties. 86 Dec 17

The incorporation of [14C]thymidine and [14C]uridine into the nucleoprotein, and [14C]phenylalanine into the protein by phytohaemagglutinin (PHA) stimulated lymphocytes from a patient with the Lesch-Nyhan syndrome [hypoxanthine-guanine phosphoribosyl transferase (EC 2.4.2.8 HGPRT) deficiency] and controls, was studied over 72 hours of incubation, with and without azaserine to block de novo purine biosynthesis. No difference was observed between the values obtained for Lesch-Nyhan and control lymphocytes, when PHA-stimulated without added azaserine. The percentage reduction in the incorporation of precursors into nucleoprotein and protein after PHA stimulation in the presence of azaserine was more obvious in the lymphocytes of the patient with the Lesch-Nyhan syndrome than in the controls after the shorter incubation periods at the lower rates of synthesis. Blocking the de novo purine biosynthetic pathway, in control PHA stimulated lymphocytes, inhibited transformation, whereas loss of the purine salvage enzyme HGPRT did not have this effect. These results are compatible with the view that the brain and bone-marrow damage that occur in the Lesch-Nyhan syndrome are the result of lack of HGPRT in tissues with little de novo purine biosynthetic capability. Other tissues with both pruine biosynthetic and salvage pathways are less vulnerable to the enzyme defect. Some possible mechanisms by which HGPRT deficiency could act are discussed. We suggest that inability to increase the supply of guanylic acid (GMP) in response to a mitotic stimulus may mediate the effect of HGPRT deficiency.
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PMID:Use of phytohaemagglutinin stimulated lymphocytes to study effects of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency on polynucleotide and protein synthesis in the Lesch-Nyhan syndrome. 93 18

Animal and in vitro studies have implicated decreased protein synthesis in the pathogenesis of tissue damage in phenylketonuria (PKU) and of growth failure in Lesch-Nyhan syndrome. Protein turnover was measured in vivo in ten young adult subjects with classical PKU, two subjects with hyperphenylalaninemia, and three children with Lesch-Nyhan syndrome using techniques based on continuous infusions of [13C]leucine and, in Lesch-Nyhan subjects, [2H5]phenylalanine. The PKU subjects had various degrees of dietary phenylalanine restriction and plasma phenylalanine levels at the time of study ranged from 450-1540 mumol/L (mean 1106). Plasma phenylalanine in the two hyperphenylalaninemic subjects was 533 and 402 mumol/L. Rates of protein synthesis in all PKU subjects (mean 3.71 g/kg/24 h, range 2.68-5.10, [13C]leucine as tracer) were in a range similar to or above control values (mean 2.97, range 2.78-3.22, n = 6), as were rates of protein catabolism (PKU mean 4.23 g/kg/24 h, range 3.15-5.45; controls 3.64, 3.50-3.91). Protein turnover values in hyperphenylalaninemia were also similar to those in controls. With [13C]leucine as tracer, both mean protein synthesis and catabolism values in Lesch-Nyhan subjects (mean 4.80 and 5.64 g/kg/24 h, respectively) were higher than values in control children matched for protein intake (synthesis 4.32 +/- 0.74 (SD) and catabolism 4.85 +/- 0.57 (g/kg/24 h, n = 5). Similar results were obtained in Lesch-Nyhan subjects using [2H5]phenylalanine as tracer. These results suggest that protein turnover is not decreased in either PKU or Lesch-Nyhan syndrome. This conclusion is inconsistent with the hypothesis that tissue damage in PKU results from impaired protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Protein metabolism in phenylketonuria and Lesch-Nyhan syndrome. 223 21

The molecular basis for complete hypoxanthine guanine phosphoribosyltransferase (HPRT) deficiency has been determined in a patient with Lesch-Nyhan syndrome. A B-lymphoblastoid cell line derived from this patient expresses normal amounts of HPRT mRNA yet no detectable immunoreactive protein as determined by radioimmunoassay. These findings suggest either a decreased rate of translation or accelerated degradation due to enhanced proteolytic susceptibility. cDNAs synthesized from this patient's RNA have a single nucleotide (nt) substitution, a C----A transversion at nt 222. RNase A cleavage analysis confirms the presence of a mutation at this position within mRNA isolated from lymphoblasts from patient A.C. This transversion predicts a phenylalanine to leucine replacement at amino acid position 73 in the translated protein. We have designated this mutant HPRTFlint. The mutation in HPRTFlint disrupts a strongly conserved region among PRTases from Escherichia coli, rodents and man, suggesting an important role for this region for the normal function of HPRT. Since it is unlikely that this amino acid substitution alters the translational rate, we hypothesize that disruption of the secondary structure within this region renders HPRTFlint more susceptible to proteolysis.
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PMID:Genetic basis of hypoxanthine guanine phosphoribosyltransferase deficiency in a patient with the Lesch-Nyhan syndrome (HPRTFlint). 338 38

Human leukocytes, which contain monocytes and neutrophils that exhibit chemotaxis to fMet-Leu-Phe, were fused with the mouse macrophage RAW264-TG3 cell line, which exhibits chemotaxis to endotoxin-activated mouse serum but not to fMet-Leu-Phe. From such fusions twelve cell lines were isolated, all of which migrated to endotoxin-activated mouse serum. Four of the cell lines also exhibited chemotaxis to fMet-Leu-Phe, and of these cell lines, only one, WBC264-9, retained the capacity to migrate to fMet-Leu-Phe after culture for 20 or more passages. Determination of the number of chromosomes and analysis of the electrofocusing patterns of human and mouse hypoxanthine-guanine phosphoribosyltransferase activity showed that WBC264-9 was derived from a human-mouse cell fusion. WBC264-9, a stable macrophage cell line that exhibits chemotaxis to fMet-Leu-Phe, provides a model system to investigate attractant-specific biochemical reactions.
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PMID:A human-mouse hybrid cell line that stably expresses chemotaxis to N-formylmethionyl-leucyl-phenylalanine. 374 19

Hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) from beef brain has been purified 3100-fold to apparent homogeneity using a purification procedure based on GMP-Sepharose affinity chromatography. The native enzyme has a molecular weight of 84,000 as determined by gel filtration studies. A subunit molecular weight of 26,000 was obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting that the enzyme is a trimer. Two forms of the enzyme have been separated by nondenaturing polyacrylamide gel electrophoresis and isoelectric focusing. Basic pI values of 7.85 and 8.10 were obtained for the two forms. These values are much higher than have been observed with any other purified phosphoribosyltransferase. The amino acid composition of the enzyme is 18 Lys, 6 His, 9 Arg, 1 Trp, 6 Cys, 28 Asx, 12 Thr, 16 Ser, 19 Glx, 10 Pro, 23 Gly, 16 Ala, 17 Val, 5 Met, 11 Ile, 19 Leu, 9 Tyr, and 8 Phe. An unusual basic amino acid, yet to be identified, was also present. The enzyme exhibits Km values of 0.42 microM for guanine, 0.99 microM for hypoxanthine, 18.6 microM for P-Rib-PP in the presence of guanine, and 2.9 microM for P-Rib-PP in the presence of hypoxanthine.
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PMID:Studies of an unusually basic hypoxanthine-guanine phosphoribosyltransferase. 735 77

Treatment of circulating human neutrophils with recombinant human granulocyte colony-stimulating factor (rhG-CSF) for 30 min augmented superoxide generation and chemotaxis induced by N-formylmethionyl-leucyl-phenylalanine (fMLP) in a dose dependent manner. When neutrophils were treated with 1 microM of methotrexate (MTX) for 60 min after incubation with rhG-CSF (10 ng/ml), the effects of rhG-CSF on superoxide generation and chemotaxis were inhibited by approximately 49 and 29%, respectively. Although inhibitory effects of MTX were also seen in neutrophils not pretreated with rhG-CSF, the degree of inhibition was much less. The addition of either hypoxanthine or guanosine at a concentration of 100 microM to the culture medium significantly attenuated the effects of MTX. However, in neutrophils obtained from a patient with Lesch-Nyhan syndrome, which lacked hypoxanthine-guanine phosphoribosyl transferase activity neither hypoxanthine nor guanosine had any rescue effect. These results suggest that MTX inhibits superoxide generation and chemotaxis in rhG-CSF-activated neutrophils, at least in part, by disturbing purine nucleotide biosynthesis.
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PMID:Methotrexate inhibits superoxide production and chemotaxis in neutrophils activated by granulocyte colony-stimulating factor. 864 14

Nucleotide metabolism was studied in erythrocytes of a mentally retarded child and family members. Partial hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency was found in the propositus and an asymptomatic maternal uncle. Studies in crude lysates demonstrated decreased apparent V(max) and slightly decreased apparent K(m) for hypoxanthine in both HPRT-deficient subjects. Genomic DNA analysis revealed a single nucleotide change with leucine-147 to phenylalanine substitution in both subjects; mother and grandmother were heterozygous carriers of the same defect. This new variant has been termed HPRT(Potenza). Increased erythrocyte concentration of NAD and rate of synthesis by intact erythrocytes were found in the patient; increased activities of nicotinic acid phosphoribosyltransferase (NAPRT) and NAD synthetase (NADs) were demonstrated in erythrocyte lysates, with normal apparent K(m) for their substrates and increased V(max). These alterations were not found in any member of the family, including the HPRT-deficient uncle. These findings show multiple derangement of nucleotide metabolism associated with partial HPRT deficiency. The enzyme alteration was presumably not the cause of neurological impairment since no neurological symptoms were found in the HPRT-deficient uncle, whereas they were present in the propositus' elder brother who had normal HPRT activity.
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PMID:Biochemical and molecular study of mentally retarded patient with partial deficiency of hypoxanthine-guanine phosphoribosyltransferase. 1200 23

Hypoxanthine-guanine phosphoribosyltransferase (HPRT) is an enzyme that catalyses the conversion of hypoxanthine and guanine into their respective nucleotides. Inherited deficiency of the enzyme is associated with a loss of striatal dopamine in both mouse and man. Although HPRT is not directly involved in the metabolism of dopamine, it contributes to the supply of GTP, which is used in the first and rate-limiting step in the synthesis of tetrahydrobiopterin (BH4). Since BH4 is required as a cofactor for tyrosine hydroxylase in the synthesis of dopamine, any limitation in the supply of GTP could interfere with the synthesis of dopamine. The current studies were designed to address the hypothesis that the reduced striatal dopamine in mice with HPRT deficiency results from reduced availability of BH4. The mutant mice had small reductions in striatal BH4, with normal BH4 levels in other brain regions. Liver BH4 was normal in HPRT-deficient mutant mice, and a phenylalanine challenge test failed to reveal any evidence for impaired hepatic phenylalanine hydroxylase, another BH4-dependent enzyme. Although striatal BH4 content is not normal, supplementation with BH4 or L-dopa failed to correct the striatal dopamine deficiency of the mutant mice, suggesting that BH4 limitation is not responsible for the dopamine loss.
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PMID:Tetrahydrobiopterin deficiency and dopamine loss in a genetic mouse model of Lesch-Nyhan disease. 1515 47

Plasmodium falciparum (Pf) hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is a potential therapeutic target. Compared to structurally homologous human enzymes, it has expanded substrate specificity. In this study, 9-deazapurines are used as in situ probes of the active sites of human and Pf HGPRTs. Through the use of these probes it is found that non-covalent interactions stabilise the pre-transition state of the HGPRT-catalysed reaction. Vibrational spectra reveal that the bound substrates are extensively distorted, the carbonyl bond of nucleobase moiety is weakened and the substrate is destabilised along the reaction coordinate. Raman shifts of the human and Pf enzymes are used to quantify the differing degrees of hydrogen bonding in the homologues. A decreased Raman cross-section in enzyme-bound 9-deazaguanine (9DAG) shows that the phenylalanine residue (Phe186 in human and Phe197 in Pf) of HGPRT stacks with the nucleobase. Differential loss of the Raman cross-section suggests that the active site is more compact in human HGPRT as compared to the Pf enzyme, and is more so in the phosphoribosyl pyrophosphate (PRPP) complex 9DAG-PRPP-HGPRT than in 9-deazahypoxanthine (9DAH)-PRPP-HGPRT.
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PMID:Differential Distortion of Purine Substrates by Human and Plasmodium falciparum Hypoxanthine-Guanine Phosphoribosyltransferase to Catalyse the Formation of Mononucleotides. 2594 19


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