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  • Articles: DFG German National Licenses  (4)
  • Erythrocytes  (3)
  • Phenylketonuria  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Atypical phenylketonuria with “dihydrobiopterin synthetase” deficiency: Absence of phosphate-eliminating enzyme activity demonstrated in liver (1985)
    Springer
    European journal of pediatrics 144 (1985), S. 13-16 
    Details
    ISSN: 1432-1076
    Keywords: Phenylketonuria ; Biopterin ; Dihydrobiopterin ; Inborn errors of metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An assay for the phosphate-eliminating enzyme (PEE) activity in liver was developed which required only 5–10 mg tissue. PEE catalyses the elimination of inorganic triphosphate from dihydroneopterin triphosphate, which is the second and irreversible step in the biosynthesis of tetrahydrobiopterin (BH4). In the presence of substrate, magnesium, NADPH, and a sepiapterin reductase fraction from human liver, PEE catalysed the formation of BH4 which was measured by HPLC and electrochemical detection. In adult human liver, a PEE activity of 1.02±0.134 μU/mg protein (mean ±1 SD; n=5) was observed. In liver needle biopsy material from five patients with defective biopterin biosynthesis, no PEE activity was found (less than 2% and 6% of the control values, respectively). The presence of an endogenous inhibitor was excluded. In a patient who died without definite diagnosis and in a patient with β-thalassaemia liver PEE activity was increased. Sepiapterin reductase activity was present in all cases. Results indicate that in “dihydrobiopterin synthetase” deficiency, the most frequent of the rare BH4-deficient variants of hyperphenylalaninaemia, the molecular defect consists in a defect of PEE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00491917
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    “Peripheral” tetrahydrobiopterin deficiency with hyperphenylalaninaemia due to incomplete 6-pyruvoyl tetrahydropterin synthase deficiency or heterozygosity (1987)
    Springer
    European journal of pediatrics 146 (1987), S. 228-232 
    Details
    ISSN: 1432-1076
    Keywords: Hyperphenylalaninaemia ; Biopterin ; 6-Pyruvoyl tetrahydropterin synthase ; Peripheral tetrahydrobiopterin deficiency ; Erythrocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four patients in three families with “peripheral” tetrahydrobiopterin deficiency were investigated. They were characterized biochemically by a tetrahydrobiopterin-responsive hyperphenylalaninaemia, a high neopterin/biopterin ratio in urine and plasma, and normal or elevated concentrations of biopterin, homovanillic acid, and 5-hydroxyindole acetic acid in cerebrospinal fluid. From measurements of the activity of erythrocyte 6-pyruvoyl tetrahydropterin synthase (PTS, formerly called phosphate-eliminating enzyme) and phenylalanine loading tests in the patients and their parets, one patient was demonstrated to be heterozygous for PTS deficiency. The others were obviously genetic compounds (allelism) with incomplete PTS deficiency. Three of the children developed normally, two of them under treatment with tetrahydrobiopterin. In the latter two patients, significantly lower concentrations of biopterin, homovanillic acid, and 5-hydroxyindole acetic acid in cerebrospinal fluid were noted at age 7 months (when treatment was interrupted) than those observed at 3 and 5 weeks, respectively. The infant who is heterozygous for PTS deficiency was born small for gestational age and showed a moderately delayed psychomotor development. It is concluded that “peripheral” tetrahydrobiopterin deficiency is caused by a partial PTS deficiency with sufficient activity to cover the tetrahydrobiopterin requirement of tyrosine 3-hydroxylase and tryptophan 5-hydroxylase in brain but not enough for phenylalanine 4-hydroxylase in liver. For therapy, tetrahydrobiopterin, 2–5 mg/kg in a single oral dose per day, is recommended to keep plasma phenylalanine normal. A careful observation of the mental development is indicated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00716465
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Prenatal diagnosis of “dihydrobiopterin synthetase” deficiency, a variant form of phenylketonuria (1986)
    Springer
    European journal of pediatrics 145 (1986), S. 176-178 
    Details
    ISSN: 1432-1076
    Keywords: Phenylketonuria ; Biopterin ; Phosphate-eliminating enzyme ; 6-Pyruvoyl tetrahydropterin synthase ; Amniotic fluid ; Erythrocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Amniocentesis was performed at 19 weeks gestation in a mother who had previously delivered a boy with “dihydrobiopterin synthetase” (DHBS) deficiency. The amniotic fluid contained neopterin in high (136 nmol/l) and biopterin in very low concentrations (1.8 nmol/l). The activity of the phosphate-eliminating enzyme (PEE, also called 6-pyruvoyl tetrahydropterin synthase, substrate: 7,8-dihydroneoptein triphosphate) which is present in liver and erythrocytes and defective in DHBS deficiency, was measured in the erythrocytes of the family members. The fetal sample showed only 2% of the activity of healthy adult controls and was comparable with that of the affected sibling. Obligate heterozygotes had activities around 20% of the controls. Two fetal control samples showed even higher activities than adult erythrocytes. Sepiapterin reductase activities were normal in all cases. At autopsy, PEE deficiency was confirmed in the liver of the fetus. We concluded that DHBS deficiency (and most probably also GTP cyclohydrolase I deficiency) can be diagnosed by metabolite measurements in amniotic fluid. PEE activity is measurable in erythrocytes, although the assay needs to be improved. Since maternal tetrahydrobiopterin does not cross the placenta, treatment of a tetrahydrobiopterin-deficient fetus with tetrahydrobiopterin in utero is not possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446058
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Tetrahydrobiopterin deficiency: assay for 6-pyruvoyl-tetrahydropterin synthase activity in erythrocytes, and detection of patients and heterozygous carriers (1988)
    Springer
    European journal of pediatrics 147 (1988), S. 15-19 
    Details
    ISSN: 1432-1076
    Keywords: Biopterin biosynthesis ; Erythrocytes ; Hyperphenylalaninaemia ; 6-Pyruvoyl-tetrahydropterin synthase ; Tetrahydrobiopterin deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 6-Pyruvoyl-tetrahydropterin synthase (PTS), a key enzyme in the synthesis of tetrahydrobiopterin in man, is defective in the most frequent variant of tetrahydrobiopterin-deficient hyperphenylalaninaemia (atypical phenylketonuria). An assay for PTS activity in erythrocytes was developed. It is based on the PTS-catalysed formation of tetrahydrobiopterin from dihydroneopterin triphosphate in the presence of magnesium, sepiapterin reductase, NADPH, dihydropteridine reductase, and NADH, and fluorimetric measurement of the product as biopterin by high performance liquid chromatography (HPLC) after oxidation with iodine. The PTS activity was higher in younger erythrocytes, including reticulocytes, than in older ones. Fetal erythrocytes showed approx. four times higher activities than those of adults. Using a more purified human liver sepiapterin reductase fraction which gave a lower yield than a crude preparation, adult controls (n=8) showed a mean erythrocyte PTS activity of 17.6 (range 11.0–29.5) μU/g Hb. Nine of 11 patients with typical PTS deficiency showed activities between 0% and 8% of the mean of controls, and two of 11 showed 14% and 20%, respectively. The obligate heterozygotes (n=16) had activities of 19% (range 8%–31%) of the mean of controls, i.e., significantly less than the expected 50%. Four patients with the “peripheral” type of the disease showed 7%–10% of the mean of controls. Thus, the assay did not distinguish between patients and heterozygotes in every family. The assay is well suited to the identification of heterozygotes of PTS deficiency in family studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00442604
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    Paper (German National Licenses)
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