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)

A previously developed simple ultramicromethod has been used for the rapid prenatal diagnosis of hypoxanthine-guanine phosphoribosyl transferase (HG-PRT) deficiency. The method is based on the incubation of small numbers of visually selected, lyophilized fibroblasts (in the present study five cells per incubation) with radioactive substrate in an end volume of 0.3 microliter. Fibroblasts derived from the amniotic fluid of a 15-week male fetus in a heterozygote for the X-linked Lesch-Nyhan syndrome showed a severe degree of HG-PRT deficiency. In total 50 fibroblasts were used. The diagnosis was confirmed upon termination of the pregnancy by the demonstration of HG-PRT deficiency in fetal erythrocytes and cultured skin fibroblasts.
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PMID:Rapid prenatal diagnosis of HG-PRT deficiency using ultra-microchemical methods. 88 39

Discordance between clinical phenotype and the level of a mutant enzyme activity may reflect differences between enzyme function in vivo and that measured by the customary enzyme assays on cell extracts. In the present study, the conversion of hypoxanthine to phosphorylated products was measured in intact skin fibroblasts and in cell extracts from seven patients with mutant hypoxanthine-guanine phosphoribosyltransferase (HPRT) and six control subjects. The patient's phenotypes ranged from asymptomatic hyperuricemia to the Lesch-Nyhan syndrome. Although there was a general correlation between the HPRT activity in cell extracts assayed by the usual methods and the function of the purine salvage pathway in patients, as reflected by urinary oxypurine excretion, there were notable exceptions. A more accurate appraisal of the functioning of the pathway at the cellular level is achieved by measuring the conversion of substrate to product in the intact cell at physiological concentrations of substrates, activators, and product and metabolite inhibitors, and in a physiological ionic environment. In one of the seven patients, the standard enzyme assay indicated normal function, whereas measurements in the intact cell exposed severe dysfunction of the salvage system. In another, the standard assay suggested a severe deficiency not evident in the intact cell or in the patient.
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PMID:Hypoxanthine phosphoribosyltransferase activity in intact fibroblasts from patients with X-linked hyperuricemia. 93 96

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

The incorporation of [15N]delta-aminolaevulinic acid and [15N glycine into haemoglobin haem and early labelled bilirubin was measured in subjects with various haematological disorders. The clearance of [14C bilirubin was used to measure bilirubin production rate, and the magnitude of the various sources of bilirubin production and the percentage ineffective erythropoiesis were calculated. Ineffective erythropoiesis was found to be a major factor in the production of the anaemia in patients with the following disorders: megaloblastic anaemia associated with the Lesch-Nyhan syndrome, thalassaemia intermedia, sideroblastic anaemia, and the anaemia of chronic disorders. In three patients with iron-deficiency anaemia ineffective erythropoiesis was increased, but was of minor importance in the production of the anaemia, while in two patients with aplastic anaemia and one with macrocytosis of alcoholism there was no increase in ineffective erythropoiesis.
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PMID:Quantitation of ineffective erythropoiesis from the incorporation of [15N] delta-aminolaevulinic acid and [15N] glycin into early labelled bilirubin. II. Anaemic patients. 95 67

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

An autopsied case of the Lesch-Nyhan syndrome did not indicate the specific pathological features except delayed physical development. 2. Xanthine calculi caused by allopurinol administration scattered in the kidneys, brain, thymus, and thyroid glands, but its excretion into urine was not observed during his life. 3. Activities of hypoxanthine-guanine phosphoribosyltransferase (HGPRT) in various tissues indicate complete deficiency, but HGPRT in liver was normal.
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PMID:An autopsy case of the Lesch-Nyhan syndrome: normal HGPRT activity in liver and xanthine calculi in various tissues. 98 65

We have developed a sensitive radioimmunoassay capable of detecting and quantitating 20 ng of hypoxanthine phosphoribosyltransferase (EC 2.4.2.8; IMP:pyrophosphate phosphoribosyltransferase) protein. For this assay, hypoxanthine phosphoribosyltransferase from human erythrocytes was iodinated with 125I under mild conditions using hydrogen peroxide and lactoperoxidase attached to Sepharose-4B. Antisera prepared against homogeneous human hypoxanthine phosphoribosyltransferase precipitates the iodinated enzyme as effectively as the unlabeled enzyme. The radioimmunoassay has been used to look for hypoxanthine phosphoribosyltransferase crossreacting material in hemolysates from sixteen different patients with a marked genetic deficiency of this enzyme characteristic of the Lesch-Nyhan syndrome. Fifteen hemolysates contained no detectable (less than 1% of normal) crossreacting material. One hemolysate contained a normal amount of crossreacting material. Hypoxanthine phosphoribosyltransferase from this patient (E.S.) has been shown to be a Km mutant enzyme.
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PMID:Radioimmune determination of hypoxanthine phosphoribosyltransferase crossreacting material in erythrocytes of Lesch-Nyhan patients. 106 95

The effects of 5-hydroxytryptophan (5-HTP), a serotonin precursor, were studied in a boy with the Lesch-Nyhan syndrome. During the course of drug treatment, self-mutilation, crying, sleep state architecture, serum dopamine B-hydroxylase (DBH), and cerebrospinal fluid levels of 5-hydroxyindolylacetic acid and homovanillic acid were studied. Treatment with 5-HTP failed to affect this child's biting behavior. However, the drug significantly reduced irritability as measured by crying time. Moreover, 5-HTP may have affected sleep state architecture, making it more normal in character. Serum DBH levels were normal throughout the study. Neither the patient's mother nor his maternal grandmother showed a hypertensive response on the cold pressor test.
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PMID:The use of 5-hydroxytryptophan in a child with Lesch-Nyhan syndrome. 108 61

1. Incubation (1-4 h) of normal human washed platelets (5-11-10-8 per ml) with [8-14C] hypoxanthine at a concentration of 10-5 M resulted in a linear incorporation of radioactivity into adenine and guanine nucleotides. 2. Washed platelets from patients with Lesch-Nyhan syndrome, deficient in hypoxanthine: guanine phosphoribosyltransferase, failed to demonstrate any significant incorporation of [8-14C] hypoxanthine but did incorporate [8-14C] adenine like normal platelets under the same incubation condition. 3. These findings are taken to indicate that normal platelets have the enzymes necessary for salvage of hypoxanthine and that hypoxanthine: guanine phosphoribosyltransferase is the obligatory first step in this pathway.
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PMID:Incorporation of hypoxanthine into adenine and guanine nucleotides by human platelets. 111 80

The Lesch-Nyhan syndrome is a rare inborn error of purine metabolism associated with hyperuricacidemia, mental retardation, and an insatiable urge for self-mutilation, especially of the extremities. Insensitivity to pain and severe muscle spasms create very difficult management problems, especially for children being cared for at home. Fortunately this syndrome is rare (1 per 380,000 live births). Four known patients are under treatment in Manitoba, of which two brothers are the subject of this study. In general, the medical management of these patients has been unsuccessful, especially in controlling self-mutilation. It therefore was decided to manage these children by the use of mechanical aids. Through the utilization of custom-designed seating devices control of the self-mutilation has been obtained, reducing the burden of family care. It is now possible for the children to attend regular school on a half-day basis. They are also able to engage in community activities without the fear that a mishap will occur when not under the vigilance of the immediate family.
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PMID:Special devices as aids in the management of child self-mutilation in the Lesch-Nyhan syndrome. 113 85


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