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Nenad Blau - One of the best experts on this subject based on the ideXlab platform.

  • altered tetrahydroBiopterin metabolism in patients with phenylalanine hydroxylase deficiency
    European Journal of Pediatrics, 2017
    Co-Authors: Francesca Nardecchia, Nenad Blau, Flavia Chiarotti, Claudia Carducci, Silvia Santagata, Giulia Valentini, Antonio Angeloni, Vincenzo Leuzzi
    Abstract:

    The tetrahydroBiopterin (BH4) cofactor is essential for the activity of various enzymes, including phenylalanine (Phe) hydroxylase. In phenylketonuria (PKU) patients, who are chronically exposed to high Phe levels, high urinary excretion of BH4 metabolites neopterin and Biopterin is observed. The aim of this longitudinal study was to investigate consistence and variability of the urinary excretion of pterins (neopterin and Biopterin) in PKU patients in relation to age and concomitant blood Phe and tyrosine levels. The study was based on the result of 274 pterin examinations (3–13 exams per subject) performed in 47 PKU patients (aged 6 days to 37 years). Multivariate analysis showed that urinary Biopterin and neopterin excretion was affected by age and concomitant blood Phe concentration. The influence of blood Phe on both Biopterin and neopterin levels was greater in patients younger than 4 months. Later on, interindividual variability was higher than intraindividual variability for both Biopterin and neopterin.

  • diagnosis of tetrahydroBiopterin deficiency using filter paper blood spots further development of the method and 5 years experience
    Journal of Inherited Metabolic Disease, 2011
    Co-Authors: Thomas Opladen, Beat Thony, Bettina Abu Seda, Anahita Rassi, Georg F Hoffmann, Nenad Blau
    Abstract:

    In every newborn with even mild hyperphenyla- laninemia (HPA) tetrahydroBiopterin (BH4) deficiencies need to be excluded as soon as possible. Differential diagnosis is most commonly performed by analysis of urinary neopterin and Biopterin. In 2005 a new method for the measurement of neopterin, Biopterin and other pterins in dried blood spot (DBS) on filter paper was introduced. In order to evaluate the usefulness of this method as a standard tool for differential diagnosis of HPAs we analyzed neopterin, Biopterin, pterin and dihydropteridine reduc- tase activity in DBS from 362 patients with HPA over the period of five years. Age-dependent reference values were established for the HPA population. Sixty-four patients with BH4 deficiency (27 patients with 6- pyruvoyl-tetrahydropterin synthase deficiency, seven with GTP cyclohydrolase I deficiency, and 30 with dihydrop- teridine reductase) were identified. Reference values for neopterin and Biopterin in DBS were calculated for each of the variants. 6-pyruvoyl-tetrahydropterin synthase and GTP cyclohydrolase I deficiency can be diagnosed by neopterin and Biopterin analysis alone, while for diagnosis of dihydropteridine reductase deficiency additional deter- mination of enzyme activity from the same DBS is essential. Regarding test sensitivity, the interpretation of neopterin and Biopterin concentration per hemoglobin is more valid than the interpretation of neopterin and Biopterin per liter. Percentage of Biopterin, of the sum of neopterin and Biopterin should always be calculated. In addition, determination of hemoglobin concentration is essential as a measure for efficient extraction of neopterin and Biopterin. Although the measurement of neopterin and Biopterin in urine is more sensitive due to the higher concentrations present, our data prove the usefulness of their measurement from DBS for the routine diagnosis of BH4 deficiencies. Abbreviations

  • plasma tetrahydroBiopterin and its pharmacokinetic following oral administration
    Molecular Genetics and Metabolism, 2004
    Co-Authors: Betina Fiege, L Kierat, Beat Thony, Bernhard Schircks, Diana Ballhausen, Walter Leimbacher, Dimitri Goriounov, Nenad Blau
    Abstract:

    TetrahydroBiopterin (BH(4)) is widely used as a therapeutic agent in patients with BH(4) deficiencies and mild forms of phenylketonuria (PKU) and there is an increasing need for the measurement of its plasma concentrations in patients with cardiovascular disorders. We measured BH(4) and total Biopterin in dithioerythritol (DTE) pretreated plasma from four adults after oral administration of BH(4) (2, 10, and 20mg/kg body weight) using the differential iodine oxidation method. About 80% (range 64.8-92.2% ) of total Biopterin was found as BH(4) when analyzed immediately after blood sampling. Compared with ascorbic acid as an antioxidant, DTE was more protective against oxidation of BH(4), particularly in samples stored over a period of 8 months. Without antioxidant (DTE or ascorbic acid) almost no BH(4) was detected. Furthermore, BH(4) and total Biopterin were measured at different time intervals (up to 33 h after oral administration) and pharmacokinetic parameters T(max) (1-4h), C(max) (258.7-259.0 nmol/L Biopterin at a dosage of 10mg/kg), and area under the curve (AUC=1708-1958 nmol(*)h/L up to T=10h) were estimated. The elimination half-life time was calculated to be 3.3-5.1h. Doubling the BH(4) dosage to 20mg/kg resulted in 60% higher AUC while sublingual BH(4) application (2mg/kg) resulted in 58-76% higher BH(4) plasma concentrations when compared with oral administration. These preliminary data suggest that in patients with BH(4) cofactor defects and BH(4)-responsive phenylalanine hydroxylase deficiency, BH(4) should be given in at least two to three daily doses and that sublingual administration may lower the required BH(4) dosage and subsequently the cost of treatment. Due to inter individual differences in pharmacokinetic properties, in some patients with hyperphenylalaninemia and mild PKU plasma BH(4) levels may be not high enough to fully activate the liver phenylalanine hydroxylase and thus lower blood phenylalanine levels. Assessment of plasma BH(4) or total Biopterin concentrations may be a good way to control the efficacy of the loading test.

  • possible impact of tetrahydroBiopterin and sepiapterin on endothelial dysfunction
    Arteriosclerosis Thrombosis and Vascular Biology, 2003
    Co-Authors: Nenad Blau, Beat Thony
    Abstract:

    To the Editor: Vasquez-Vivar et al1 reported on diminished tetrahydroBiopterin (BH4) concentrations in vessels from hypercholesterolemic rabbits. This is an interesting finding because both in serum and urine from patients with coronary artery diseases and hypercholesterolemia, total plasma Biopterin concentrations were found to be unchanged2 (unpublished data, 2002). However, total Biopterin represents the sum of BH4, 7,8-dihydrobipterin (BH2), and fully oxidized Biopterin, and one cannot exclude possible the effect of either reduced BH4 or increased BH2 concentrations on the endothelial dysfunction in these patients. In normal plasma, almost all Biopterin (>95%) is present as BH4, and measurement of biologically active tetrahydro-derivative seems to be essential. Differential oxidation with iodine and subsequent high-pressure liquid chromatography (HPLC), according to Fukushima and Nixon,3 is a simple method to measure different oxidation forms of Biopterin. In this method, under acidic conditions, BH4 and BH2 are oxidized to Biopterin, while under basic conditions, only BH2 is oxidized to Biopterin, and BH4 undergoes a side-chain cleavage to form the blue fluorescing pterin. The difference in Biopterin content between the two oxidations represents the actual BH4 levels. HPLC separation of Biopterin from pterin and isoxanthopterin is essential for the correct interpretation. Another important finding of Vasquez-Vivar et al1 is the observation that supplementation with sepiapterin, an intermediate in the salvage pathway of …

Bernd Mayer - One of the best experts on this subject based on the ideXlab platform.

  • identification of the 4 amino analogue of tetrahydroBiopterin as a dihydropteridine reductase inhibitor and a potent pteridine antagonist of rat neuronal nitric oxide synthase
    Biochemical Journal, 1996
    Co-Authors: Ernst R. Werner, Kurt Schmidt, Eva Pitters, Helmut Wachter, Gabriele Wernerfelmayer, Bernd Mayer
    Abstract:

    The binding of tetrahydropteridines with 6-di- and trihydroxypropyl side chains to recombinant rat neuronal nitric oxide (NO) synthase (EC 1.14.13.39) was determined by competition with 6R-[3'-3H]-5,6,7,8-tetrahydro-L-erythro-Biopterin (6R-[3'-3H]H4Biopterin). Although all but one of the derivatives exhibited only poor affinities (Ki 50 microM), the 4-amino analogue of 6R-H4 Biopterin was a potent antagonist of 6R-H4 Biopterin binding (Ki 13.2 nM). The 4-amino analogue of 6R-H4 Biopterin inhibited NO synthase stimulation by the natural cofactor 6R-H4 Biopterin with an IC50 of 1 microM without affecting the basal activity observed in the absence of added 6R-H4 Biopterin. Because the 4-amino analogue of 6R-H4Biopterin also inhibited dihydropteridine reductase (EC 1.6.99.7; IC50 20 microM), our results support the hypothesis that redox cycling of H4 Biopterin might be required for the NO synthase reaction.

  • the pteridine binding site of brain nitric oxide synthase tetrahydroBiopterin binding kinetics specificity and allosteric interaction with the substrate domain
    Journal of Biological Chemistry, 1994
    Co-Authors: Peter Klatt, Ernst R. Werner, Kurt Schmidt, M Schmid, Eva Leopold, Bernd Mayer
    Abstract:

    Nitric oxide (NO) synthases contain FAD, FMN, heme, and (6R)-5,6,7,8-tetrahydro-L-Biopterin as prosthetic groups. We have characterized the pteridine-binding site of purified brain NO synthase, using 3H-labeled (6R)-5,6,7,8-tetrahydro-L-Biopterin as radioligand. Association of [3H]tetrahydroBiopterin followed second-order kinetics (kon = 1.3 x 10(6) M-1 min-1), the dissociation reaction was reversible and first-order (koff = 3.2 x 10(-1) min-1), yielding a kinetic KD of 0.25 microM. Binding of the radioligand was competitively antagonized by several pteridine derivatives with the following order of potency (KI): 7,8-dihydro-L-Biopterin (2.2 microM), (6S)-5,6,7,8-tetrahydro-L-Biopterin (19 microM), (6R,S)-6-methyl-5,6,7,8-tetrahydropterin (240 microM), and 6,7-dimethyl-5,6,7,8-tetrahydropterin (> 1 mM). The affinity of NO synthase for tetrahydroBiopterin was increased 6-fold in the presence of 0.1 mM L-arginine (KD = 37 nM), and, conversely, tetrahydroBiopterin enhanced the affinity of the enzyme for 3H-labeled NG-nitro-L-arginine about 2-fold. 7-Nitroindazole, which presumably binds to the heme group of NO synthase, competitively inhibited binding of [3H]tetrahydroBiopterin and [3H]NG-nitro-L-arginine with similar Ki values (0.1 microM). Functional as well as binding studies revealed that 7-nitroindazole was competitive with both L-arginine and tetrahydroBiopterin. Our data indicate that brain NO synthase exhibits a highly specific binding site for (6R)-5,6,7,8-tetrahydro-L-Biopterin, which allosterically interacts with the substrate domain and may be located proximal to the prosthetic heme group of NO synthase.

  • brain nitric oxide synthase is a Biopterin and flavin containing multi functional oxido reductase
    FEBS Letters, 1991
    Co-Authors: Bernd Mayer, Ernst R. Werner, Helmut Wachter, M John, Burghard Heinzel, Gunter Schultz, Eycke Bohme
    Abstract:

    Brain nitric oxide synthase is a Ca2+/calmodulin-regulated enzyme which converts L-arginine into NO. Enzymatic activity of this enzyme essentially depends on NADPH and is stimulated by tetrahydroBiopterin (H4Biopterin). We found that purified NO synthase contains enzyme-bound H4 Biopterin, explaining the enzymatic activity observed in the absence of added cofactor. Together with the finding that H4 Biopterin was effective at substoichiometrical concentrations, these results indicate that NO synthase essentially depends on H4 Biopterin as a cofactor which is recycled during enzymatic NO formation. We found that the purified enzyme also contains FAD, FMN and non-heme iron in equimolar amounts and exhibits striking activities, including a Ca2+/calmodulin-dependent NADPH oxidase activity, leading to the formation of hydrogen peroxide at suboptimal concentrations of L-arginine or H4 Biopterin.

Tadashi Matsunaga - One of the best experts on this subject based on the ideXlab platform.

Torbjoern G Nygaard - One of the best experts on this subject based on the ideXlab platform.

  • brain Biopterin and tyrosine hydroxylase in asymptomatic dopa responsive dystonia
    Annals of Neurology, 2002
    Co-Authors: Yoshiaki Furukawa, Gregory Kapatos, John W Haycock, Julian Worsley, Henry Wong, Stephen J Kish, Torbjoern G Nygaard
    Abstract:

    It is assumed that brain Biopterin and dopamine loss should not be as severe in asymptomatic dopa-responsive dystonia caused by GCH1 mutations as it is in symptomatic dopa-responsive dystonia. However, the actual status of dopaminergic systems in asymptomatic cases is unknown. In the autopsied putamen of an asymptomatic GCH1 mutation carrier, we found that brain Biopterin loss (-82%) paralleled that reported in dopa-responsive dystonia patients (-84%). However, tyrosine hydroxylase protein and dopamine levels (-52 and -44%, respectively) were not as severely affected as in symptomatic patients (exceeding -97 and -88%, respectively). Our data suggest that the extent of striatal tyrosine hydroxylase protein loss may be critical in determining dopa-responsive dystonia symptomatology.

Ernst R. Werner - One of the best experts on this subject based on the ideXlab platform.

  • cerebrospinal fluid levels of Biopterin nitric oxide metabolites and immune activation markers and the clinical course of human cerebral malaria
    The Journal of Infectious Diseases, 1998
    Co-Authors: Gunter Weiss, Ernst R. Werner, Philip E Thuma, Godfrey Biemba, George F Mabeza, Victor R Gordeuk
    Abstract:

    Cerebrospinal fluid samples from 130 children who presented with cerebral malaria were investigated to elucidate the impact of Biopterin production, NO formation, and local immune activation on the clinical course of this disease. Biopterin levels were significantly lower in patients who were in a deeper coma (P = .02). Cerebrospinal fluid concentrations of NO were significantly higher in children who died than in survivors (P = .037); however, this was not the case for macrophage activation markers, neopterin, and soluble tumor necrosis factor receptor p75 (sTNFR-75). Biopterin, neopterin, and sTNFR-75 but not NO concentrations were significantly related to each other. Low Biopterin levels in deep coma are compatible with an impaired local Th1 response, but the low levels could also be due to the scavenging of radicals or to decreased neurotransmitter synthesis. Local production of NO, most likely by nonimmune mechanisms, may be detrimental in cerebral malaria; however, this appears not to be the case for local Th1-mediated immune pathways.

  • identification of the 4 amino analogue of tetrahydroBiopterin as a dihydropteridine reductase inhibitor and a potent pteridine antagonist of rat neuronal nitric oxide synthase
    Biochemical Journal, 1996
    Co-Authors: Ernst R. Werner, Kurt Schmidt, Eva Pitters, Helmut Wachter, Gabriele Wernerfelmayer, Bernd Mayer
    Abstract:

    The binding of tetrahydropteridines with 6-di- and trihydroxypropyl side chains to recombinant rat neuronal nitric oxide (NO) synthase (EC 1.14.13.39) was determined by competition with 6R-[3'-3H]-5,6,7,8-tetrahydro-L-erythro-Biopterin (6R-[3'-3H]H4Biopterin). Although all but one of the derivatives exhibited only poor affinities (Ki 50 microM), the 4-amino analogue of 6R-H4 Biopterin was a potent antagonist of 6R-H4 Biopterin binding (Ki 13.2 nM). The 4-amino analogue of 6R-H4 Biopterin inhibited NO synthase stimulation by the natural cofactor 6R-H4 Biopterin with an IC50 of 1 microM without affecting the basal activity observed in the absence of added 6R-H4 Biopterin. Because the 4-amino analogue of 6R-H4Biopterin also inhibited dihydropteridine reductase (EC 1.6.99.7; IC50 20 microM), our results support the hypothesis that redox cycling of H4 Biopterin might be required for the NO synthase reaction.

  • the pteridine binding site of brain nitric oxide synthase tetrahydroBiopterin binding kinetics specificity and allosteric interaction with the substrate domain
    Journal of Biological Chemistry, 1994
    Co-Authors: Peter Klatt, Ernst R. Werner, Kurt Schmidt, M Schmid, Eva Leopold, Bernd Mayer
    Abstract:

    Nitric oxide (NO) synthases contain FAD, FMN, heme, and (6R)-5,6,7,8-tetrahydro-L-Biopterin as prosthetic groups. We have characterized the pteridine-binding site of purified brain NO synthase, using 3H-labeled (6R)-5,6,7,8-tetrahydro-L-Biopterin as radioligand. Association of [3H]tetrahydroBiopterin followed second-order kinetics (kon = 1.3 x 10(6) M-1 min-1), the dissociation reaction was reversible and first-order (koff = 3.2 x 10(-1) min-1), yielding a kinetic KD of 0.25 microM. Binding of the radioligand was competitively antagonized by several pteridine derivatives with the following order of potency (KI): 7,8-dihydro-L-Biopterin (2.2 microM), (6S)-5,6,7,8-tetrahydro-L-Biopterin (19 microM), (6R,S)-6-methyl-5,6,7,8-tetrahydropterin (240 microM), and 6,7-dimethyl-5,6,7,8-tetrahydropterin (> 1 mM). The affinity of NO synthase for tetrahydroBiopterin was increased 6-fold in the presence of 0.1 mM L-arginine (KD = 37 nM), and, conversely, tetrahydroBiopterin enhanced the affinity of the enzyme for 3H-labeled NG-nitro-L-arginine about 2-fold. 7-Nitroindazole, which presumably binds to the heme group of NO synthase, competitively inhibited binding of [3H]tetrahydroBiopterin and [3H]NG-nitro-L-arginine with similar Ki values (0.1 microM). Functional as well as binding studies revealed that 7-nitroindazole was competitive with both L-arginine and tetrahydroBiopterin. Our data indicate that brain NO synthase exhibits a highly specific binding site for (6R)-5,6,7,8-tetrahydro-L-Biopterin, which allosterically interacts with the substrate domain and may be located proximal to the prosthetic heme group of NO synthase.

  • brain nitric oxide synthase is a Biopterin and flavin containing multi functional oxido reductase
    FEBS Letters, 1991
    Co-Authors: Bernd Mayer, Ernst R. Werner, Helmut Wachter, M John, Burghard Heinzel, Gunter Schultz, Eycke Bohme
    Abstract:

    Brain nitric oxide synthase is a Ca2+/calmodulin-regulated enzyme which converts L-arginine into NO. Enzymatic activity of this enzyme essentially depends on NADPH and is stimulated by tetrahydroBiopterin (H4Biopterin). We found that purified NO synthase contains enzyme-bound H4 Biopterin, explaining the enzymatic activity observed in the absence of added cofactor. Together with the finding that H4 Biopterin was effective at substoichiometrical concentrations, these results indicate that NO synthase essentially depends on H4 Biopterin as a cofactor which is recycled during enzymatic NO formation. We found that the purified enzyme also contains FAD, FMN and non-heme iron in equimolar amounts and exhibits striking activities, including a Ca2+/calmodulin-dependent NADPH oxidase activity, leading to the formation of hydrogen peroxide at suboptimal concentrations of L-arginine or H4 Biopterin.