Tetrahydrobiopterin Deficiency: From Phenotype to Genotype

Blau, Nenad; Thöny, Beat; Heizmann, Claus W.; Dhondt, Jean-Louis

doi:10.1515/pteridines.1993.4.1.1

Cited by 73 publications

(41 citation statements)

References 19 publications

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“…Inherited 6-pyruvoyl tetrahydropterin synthase (PTPS) deficiency is the most frequent cause of an impaired metabolism of BH, [5]. The lack of BH, leads to hyperphenylalaninemia accompanied by severe progressive mental retardation [6].…”

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confidence: 99%

Expression and characterization of recombinant human and rat liver 6‐pyruvoyl tetrahydropterin synthase

Bürgisser

Thöny

Redweik

et al. 1994

European Journal of Biochemistry

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6-Pyruvoyl-tetrahydropterin synthase is the rate-limiting enzyme in the synthesis of human tetrahydrobiopterin, a cofactor for several hydroxylases involved in catecholamine and serotonin biosynthesis. The human and rat liver cDNAs encoding the 16-kDa subunit of 6-pyruvoyl tetrahydropterin synthase were expressed as maltose-binding -6-pyruvoyl-tetrahydropterin-synthase fusion proteins. After cleavage from the fusion protein, the human and rat enzymes were purified to homogeneity. Apparent K, for the substrate dihydroneopterin triphosphate (8.5 pM for the human and 8.0 yM for the rat enzyme), PI (4.6 and 4.8) and heat stability of the recombinant enzymes were similar to the native enzymes. The specific activity of the enzymes was enhanced up to fourfold in the presence of dithiothreitol during purification. The modification of the only cysteine residue in rat 6-pyruvoyl tetrahydropterin synthase, which is conserved in the human enzyme, inhibited its activity up to 80%. Modification under non-reducing conditions of both cysteine residues of the human enzyme by N-ethylpyridine resulted in a 95% loss of enzyme activity. This demonstrates that the two cysteines are not linked by disulfide bridges but rather involved in catalysis. Cross-linking experiments and analysis by gel electrophoresis showed predominantly trimeric and hexameric forms of the recombinant enzymes from both species suggesting that the native form is a homohexamer of 98 kDa, for the human, and 95 kDa, for the rat enzyme, composed of two trimeric subunits.Tetrahydrobiopterin ( B b ) is the cofactor of the aromatic amino acid hydroxylases [l] and other enzymes 12-41. Inherited 6-pyruvoyl tetrahydropterin synthase (PTPS) deficiency is the most frequent cause of an impaired metabolism of BH, [5]. The lack of BH, leads to hyperphenylalaninemia accompanied by severe progressive mental retardation [6]. Changes in BH, metabolism have also been observed in different neurological disorders such as Parkinson's disease, Alzheimer's disease, dystonia, depression and others [7-101. The committing step in the biosynthesis of BH, is the conversion of GTP to dihydroneopterin triphosphate (NH,TP) by GTP cyclohydrolase I [ll]. PTPS then converts NH,TP to 6-pyruvoyl tetrahydropterin, the first tetrahydro intermediate [12]. The last step in the BH, production is the

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confidence: 99%

Expression and characterization of recombinant human and rat liver 6‐pyruvoyl tetrahydropterin synthase

Bürgisser

Thöny

Redweik

et al. 1994

European Journal of Biochemistry

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“…Therefore, even in patients with hyperphenylalaninemia with persistently high NIB ratios during infancy, it is possible to identify PTPS deficiency if there is a decrease in the NIB ratio after the serum level of phenylalanine is kept low for several days. The NIB ratios reported up to now for patients with PTPS deficiency have a lower limit of about 40 (21), and the values for healthy neonates have an upper limit of about 30, so it is possible to diagnose PTPS deficiency during the neonatal period by use of 40 as a cut-off value. However, elevated neopterin levels have been found in urine from patients with various viral infections (22), so that it is important to role out infection when diagnosis of PTPS deficiency is to be based on the NIB ratio.…”

Section: Discussionmentioning

confidence: 99%

Early Diagnosis of 6-Pyruvoyl-tetrahydropterin Synthase Deficiency

Shintaku

1994

Pteridines

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Summary 6-Pyruvoyl-tetrahydropterin synthase (PTPS) deficiency, which used to be called dihydrobiopterin synthase deficiency, is the most common kind of tetrahydrobiopterin deficiency. Early treatment by administration of tetrahydrobiopterin and neurotransmitter precursors helps to prevent neurological injury, so prompt diagnosis of neonates with hyperphenylalaninemia discovered by screening for phenylketonuria is necessary. Three patients with PTPS deficiency were diagnosed by pteridine analysis. All patients had low biopterin and high neopterin levels in the urine, resulting in a neopterin to biopterin ratio (NIB) much higher than that of age-matched controls. The mean NIB in the parents of these patients was twice that of healthy unrelated adults. PTPS activity was measured in one of these patients with PTPS deficiency and in his family members; the patient was homozygous and his parents were heterozygous for PTPS deficiency. This result meant that NIB could be used as an index of PTPS activity. In healthy subjects studied crosssectionally, urinary levels of pteridine decreased in groups of increasing age, and the same change was found in subjects with hyperphenylalaninemia studied cross-sectionally. Thus, pteridine values of patients can be compared meaningfully only with age-matched controls. The urinary N IB is useful for the diagnosis of homozygotes and heterozygotes for PTPS deficiency.

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“…Plasmid pMT3-1␣-cGK expressing the bovine tracheal smooth muscle cGKI␣ isoenzmye has been described (21). To express the murine cGKII in COS-1 cells, the corresponding 2.5-kilobase SnaBI-HindIII fragment containing a (His) 6 -tag at its 5Ј-end was first isolated from the parental pFastBac1-vector (Life Technologies) 2 and subcloned into the HincII/ HindIII-opened pUC18 vector. Subsequently, the XbaI-HindIII fragment containing the (His) 6 -cGKII-cDNA in the pUC18 polylinker was cut out and inserted into the XbaI/HindIII sites of pSCT1 to generate plasmid pSCT1-His-cGKII.…”

Section: Methodsmentioning

confidence: 99%