The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform
Michio Hirano - One of the best experts on this subject based on the ideXlab platform.
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Thymidine Phosphorylase is both a therapeutic and a suicide gene in a murine model of mitochondrial neurogastrointestinal encephalomyopathy
Gene Therapy, 2014Co-Authors: Sergio Lopez-estevez, Michio Hirano, G Ferrer, Javier Torres-torronteras, María José Mansilla, Silvia Casacuberta-serra, Lluís Martorell, Ramon Martí, Jordi BarquineroAbstract:Thymidine Phosphorylase is both a therapeutic and a suicide gene in a murine model of mitochondrial neurogastrointestinal encephalomyopathy
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Assessment of Thymidine Phosphorylase function: measurement of plasma Thymidine (and deoxyuridine) and Thymidine Phosphorylase activity.
Methods of Molecular Biology, 2011Co-Authors: Ramon Martí, Luis C. López, Michio HiranoAbstract:We describe detailed methods to measure Thymidine (dThd) and deoxyuridine (dUrd) concentrations and Thymidine Phosphorylase (TP) activity in biological samples. These protocols allow the detection of TP dysfunction in patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). Since the identification of mutations in TYMP, the gene encoding TP, as the cause of MNGIE (Nishino et al. Science 283:689-692, 1999), the assessment of TP dysfunction has become the best screening method to rule out or confirm MNGIE in patients. TYMP sequencing, to find the causative mutations, is only needed when TP dysfunction is detected. dThd and dUrd are measured by resolving these compounds with high-performance liquid chromatography (HPLC) followed by the spectrophotometric monitoring of the eluate absorbance at 267 nm (HPLC-UV). TP activity can be measured by an endpoint determination of the thymine formed after 1 h incubation of the buffy coat homogenate in the presence of a large excess of its substrate dThd, either spectrophotometrically or by HPLC-UV.
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Thymidine Phosphorylase mutations cause instability of mitochondrial dna
Gene, 2005Co-Authors: Michio Hirano, Ramon Martí, Clotilde Lagiertourenne, Maria Lucia Valentino, Yutaka NishigakiAbstract:Abstract Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by ptosis and progressive external ophthalmoplegia, peripheral neuropathy, severe gastrointestinal dysmotility, cachexia and leukoencephalopathy. Muscle biopsies of MNGIE patients have revealed morphologically abnormal mitochondria and defects of respiratory chain enzymes. In addition, patients harbor depletion, multiple deletions, and point mutations of mitochondrial DNA (mtDNA). This disorder is caused by loss-of-function mutations in the gene encoding Thymidine Phosphorylase (TP) a cytosolic enzyme. In MNGIE patients, TP activity is very low or absent resulting in dramatically elevated levels of plasma Thymidine and deoxyuridine. We have hypothesized that the increased levels of Thymidine and deoxyuridine cause mitochondrial nucleotide pool imbalances that, in turn, generate mtDNA alterations.
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Increased blood-brain barrier permeability with Thymidine Phosphorylase deficiency.
Annals of Neurology, 2004Co-Authors: Kinga Szigeti, Norbert Sule, Adekunle M. Adesina, Dawna L. Armstrong, Gulam Mustafa Saifi, Eduardo Bonilla, Michio Hirano, James R. LupskiAbstract:Mitochondrial neurogastrointestinal encephalomyopathy is an autosomal recessive multisystemic disorder caused by Thymidine Phosphorylase deficiency. Whereas the pathomechanism of the secondary mitochondrial dysfunction has been extensively studied, that of the leukoencephalopathy has not been elucidated. We hypothesized that the white matter hyperintensities on T2-weighted magnetic resonance images reflect disturbance of blood–brain barrier function. Albumin immunohistochemistry disclosed quantitative (p < 0.01) and qualitative differences between the mitochondrial neurogastrointestinal encephalomyopathy and control brains, indicating that loss of Thymidine Phosphorylase function impairs the integrity of the blood–brain barrier. Ann Neurol 2004
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elevated plasma deoxyuridine in patients with Thymidine Phosphorylase deficiency
Biochemical and Biophysical Research Communications, 2003Co-Authors: Ramon Martí, Yutaka Nishigaki, Michio HiranoAbstract:Mutations in the nuclear gene encoding Thymidine Phosphorylase (TP) cause mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), an autosomal recessive disease with mitochondrial dysfunction and mitochondrial DNA abnormalities. We have demonstrated alterations of Thymidine (dThd) metabolism in MNGIE patients. Here, we report the accumulation of another substrate of TP, deoxyuridine (dUrd), whose circulating levels ranged from 5.5 to 24.4 μM (average 14.2) in MNGIE and were undetectable (<0.05 μM) in both TP mutation carriers and controls. The dramatic accumulation of dUrd may contribute to nucleotide pool imbalances and, together with the increased levels of dThd, is likely to contribute to the pathogenesis of MNGIE.
Antonín Holý - One of the best experts on this subject based on the ideXlab platform.
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Syntheses of N3-substituted thymine acyclic nucleoside phosphonates and a comparison of their inhibitory effect towards Thymidine Phosphorylase.
Bioorganic & Medicinal Chemistry Letters, 2008Co-Authors: Karel Pomeisl, Antonín Holý, Ivan Votruba, Radek PohlAbstract:Abstract A series of N 3 -substituted thymine acyclic nucleoside phosphonates bearing a number of (phosphonomethoxy)alkyl groups were synthesized and investigated for their ability to inhibit the human Thymidine Phosphorylase expressed in V79 Chinese hamster cells, as well as Thymidine Phosphorylase from SD-lymphoma, Escherichia coli and human placenta. In comparison to N 1 - substituted analogues which possess a considerable inhibitory activity towards Thymidine Phosphorylase from SD-lymphoma, the results showed a marginal inhibitory effect of these compounds. None of the presented N 3 -substituted derivatives possess a significant cytostatic activity.
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syntheses of pyrimidine acyclic nucleoside phosphonates as potent inhibitors of Thymidine Phosphorylase pd ecgf from sd lymphoma
Nucleosides Nucleotides & Nucleic Acids, 2007Co-Authors: Karel Pomeisl, Antonín Holý, Ivan Votruba, Radek PohlAbstract:In the present study, we synthesized a series of pyrimidine acyclic nucleoside phosphonates bearing a number of substituents in C-5 position of uracil moiety and in the N-1-side chain. In addition, we have investigated in particular the novel syntheses of fluorinated derivatives substituted in the N-1-side chain and uracil C-5 position because fluorine-containing substituents are often powerful modifiers of chemical and biological properties. The obtained compounds exhibit a considerable inhibitory potency of Thymidine Phosphorylase from SD-lymphoma. In contrast, the synthesized phosphonates are not efficient inhibitors of E. coli and human Thymidine Phosphorylase.
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discovery of 5 substituted 6 chlorouracils as efficient inhibitors of human Thymidine Phosphorylase
Journal of Medicinal Chemistry, 2007Co-Authors: Radim Nencka, Ivan Votruba, H Hrebabecký, Petr Jansa, Eva Tloustova, Květa Horska, Milena Masojidkova, Antonín HolýAbstract:Thymidine Phosphorylase plays an important role in angiogenesis, which is an attractive target for therapy of cancer and other diseases. In our continuous effort to develop novel inhibitors of thym...
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Inhibition of Thymidine Phosphorylase (PD-ECGF) from SD-lymphoma by phosphonomethoxyalkyl thymines
Biochemical Pharmacology, 2005Co-Authors: Ivan Votruba, Karel Pomeisl, Antonín Holý, Eva Tloušt’ová, Otová BAbstract:Abstract A series of thymine phosphonomethoxyalkyl derivatives were evaluated for their ability to inhibit Thymidine Phosphorylase (dThdPase) purified from rat spontaneous T-cell lymphoma. A kinetic study of Thymidine phosphorolysis catalyzed by dThdPase was performed with Thymidine and/or inorganic phosphate as substrates. Data show that the substantial inhibitory effect of these acyclic nucleotide analogues is decreasing in the order of ( R )-FPMPT > ( S )-FPMPT ≥ ( R )-HPMPT > ( S )-PMPT > ( S )-HPMPT > PMET ≥ ( R )-PMPT. The inhibitory potency ( K i / dThd K m ) of the most efficient inhibitors from this series against T-cell lymphoma enzyme is 0.0026 for ( R )-FPMPT and 0.0048 for ( S )-FPMPT. The studied compounds do not inhibit Escherichia coli and human enzyme and possess lower inhibitory potency against rat liver Thymidine Phosphorylase.
Yutaka Nishigaki - One of the best experts on this subject based on the ideXlab platform.
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Thymidine Phosphorylase mutations cause instability of mitochondrial dna
Gene, 2005Co-Authors: Michio Hirano, Ramon Martí, Clotilde Lagiertourenne, Maria Lucia Valentino, Yutaka NishigakiAbstract:Abstract Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by ptosis and progressive external ophthalmoplegia, peripheral neuropathy, severe gastrointestinal dysmotility, cachexia and leukoencephalopathy. Muscle biopsies of MNGIE patients have revealed morphologically abnormal mitochondria and defects of respiratory chain enzymes. In addition, patients harbor depletion, multiple deletions, and point mutations of mitochondrial DNA (mtDNA). This disorder is caused by loss-of-function mutations in the gene encoding Thymidine Phosphorylase (TP) a cytosolic enzyme. In MNGIE patients, TP activity is very low or absent resulting in dramatically elevated levels of plasma Thymidine and deoxyuridine. We have hypothesized that the increased levels of Thymidine and deoxyuridine cause mitochondrial nucleotide pool imbalances that, in turn, generate mtDNA alterations.
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elevated plasma deoxyuridine in patients with Thymidine Phosphorylase deficiency
Biochemical and Biophysical Research Communications, 2003Co-Authors: Ramon Martí, Yutaka Nishigaki, Michio HiranoAbstract:Mutations in the nuclear gene encoding Thymidine Phosphorylase (TP) cause mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), an autosomal recessive disease with mitochondrial dysfunction and mitochondrial DNA abnormalities. We have demonstrated alterations of Thymidine (dThd) metabolism in MNGIE patients. Here, we report the accumulation of another substrate of TP, deoxyuridine (dUrd), whose circulating levels ranged from 5.5 to 24.4 μM (average 14.2) in MNGIE and were undetectable (<0.05 μM) in both TP mutation carriers and controls. The dramatic accumulation of dUrd may contribute to nucleotide pool imbalances and, together with the increased levels of dThd, is likely to contribute to the pathogenesis of MNGIE.
Ramon Martí - One of the best experts on this subject based on the ideXlab platform.
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Thymidine Phosphorylase is both a therapeutic and a suicide gene in a murine model of mitochondrial neurogastrointestinal encephalomyopathy
Gene Therapy, 2014Co-Authors: Sergio Lopez-estevez, Michio Hirano, G Ferrer, Javier Torres-torronteras, María José Mansilla, Silvia Casacuberta-serra, Lluís Martorell, Ramon Martí, Jordi BarquineroAbstract:Thymidine Phosphorylase is both a therapeutic and a suicide gene in a murine model of mitochondrial neurogastrointestinal encephalomyopathy
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Assessment of Thymidine Phosphorylase function: measurement of plasma Thymidine (and deoxyuridine) and Thymidine Phosphorylase activity.
Methods of Molecular Biology, 2011Co-Authors: Ramon Martí, Luis C. López, Michio HiranoAbstract:We describe detailed methods to measure Thymidine (dThd) and deoxyuridine (dUrd) concentrations and Thymidine Phosphorylase (TP) activity in biological samples. These protocols allow the detection of TP dysfunction in patients with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE). Since the identification of mutations in TYMP, the gene encoding TP, as the cause of MNGIE (Nishino et al. Science 283:689-692, 1999), the assessment of TP dysfunction has become the best screening method to rule out or confirm MNGIE in patients. TYMP sequencing, to find the causative mutations, is only needed when TP dysfunction is detected. dThd and dUrd are measured by resolving these compounds with high-performance liquid chromatography (HPLC) followed by the spectrophotometric monitoring of the eluate absorbance at 267 nm (HPLC-UV). TP activity can be measured by an endpoint determination of the thymine formed after 1 h incubation of the buffy coat homogenate in the presence of a large excess of its substrate dThd, either spectrophotometrically or by HPLC-UV.
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Thymidine Phosphorylase mutations cause instability of mitochondrial dna
Gene, 2005Co-Authors: Michio Hirano, Ramon Martí, Clotilde Lagiertourenne, Maria Lucia Valentino, Yutaka NishigakiAbstract:Abstract Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an autosomal recessive disorder characterized by ptosis and progressive external ophthalmoplegia, peripheral neuropathy, severe gastrointestinal dysmotility, cachexia and leukoencephalopathy. Muscle biopsies of MNGIE patients have revealed morphologically abnormal mitochondria and defects of respiratory chain enzymes. In addition, patients harbor depletion, multiple deletions, and point mutations of mitochondrial DNA (mtDNA). This disorder is caused by loss-of-function mutations in the gene encoding Thymidine Phosphorylase (TP) a cytosolic enzyme. In MNGIE patients, TP activity is very low or absent resulting in dramatically elevated levels of plasma Thymidine and deoxyuridine. We have hypothesized that the increased levels of Thymidine and deoxyuridine cause mitochondrial nucleotide pool imbalances that, in turn, generate mtDNA alterations.
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elevated plasma deoxyuridine in patients with Thymidine Phosphorylase deficiency
Biochemical and Biophysical Research Communications, 2003Co-Authors: Ramon Martí, Yutaka Nishigaki, Michio HiranoAbstract:Mutations in the nuclear gene encoding Thymidine Phosphorylase (TP) cause mitochondrial neurogastrointestinal encephalomyopathy (MNGIE), an autosomal recessive disease with mitochondrial dysfunction and mitochondrial DNA abnormalities. We have demonstrated alterations of Thymidine (dThd) metabolism in MNGIE patients. Here, we report the accumulation of another substrate of TP, deoxyuridine (dUrd), whose circulating levels ranged from 5.5 to 24.4 μM (average 14.2) in MNGIE and were undetectable (<0.05 μM) in both TP mutation carriers and controls. The dramatic accumulation of dUrd may contribute to nucleotide pool imbalances and, together with the increased levels of dThd, is likely to contribute to the pathogenesis of MNGIE.
Vern L. Schramm - One of the best experts on this subject based on the ideXlab platform.
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The synthesis of possible transition state analogue inhibitors of Thymidine Phosphorylase
Tetrahedron Letters, 2015Co-Authors: Gary B. Evans, Vern L. Schramm, Graeme J. Gainsford, Peter C. TylerAbstract:The synthetically challenging SN2 transition state mimic for Thymidine Phosphorylase, along with its phosphonate analogue, were synthesised via a modified Corey–Link reaction in good overall yields and ensuring the correct stereochemical outcome.
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Binding Causes the Remote [5‘-3H]Thymidine Kinetic Isotope Effect in Human Thymidine Phosphorylase
Journal of the American Chemical Society, 2004Co-Authors: Matthew R. Birck, Vern L. SchrammAbstract:The remote 5‘-3H V/K kinetic isotope effect (KIE) observed in human Thymidine Phosphorylase (6.1%) is significantly larger than can be explained by the reaction chemistry. One hypothesis connects the 5‘-3H KIE in purine nucleoside Phosphorylase to that enzyme's SN1 transition state. The transition state of Thymidine Phosphorylase, however, is an SN2 nucleophilic displacement. Here we report equilibrium binding isotope effects sufficiently large to explain the presence of this substantial KIE in Thymidine Phosphorylase.
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nucleophilic participation in the transition state for human Thymidine Phosphorylase
Journal of the American Chemical Society, 2004Co-Authors: Matthew R. Birck, Vern L. SchrammAbstract:Recombinant human Thymidine Phosphorylase catalyzes the reaction of arsenate with Thymidine to form thymine and 2-deoxyribose 1-arsenate, which rapidly decomposes to 2-deoxyribose and inorganic arsenate. The transition-state structure of this reaction was determined using kinetic isotope effect analysis followed by computer modeling. Experimental kinetic isotope effects were determined at physiological pH and 37 °C. The extent of forward commitment to catalysis was determined by pulse-chase experiments to be 0.70%. The intrinsic kinetic isotope effects for [1‘-3H]-, [2‘R-3H]-, [2‘S-3H]-, [4‘-3H]-, [5‘-3H]-, [1‘-14C]-, and [1-15N]-Thymidines were determined to be 0.989 ± 0.002, 0.974 ± 0.002, 1.036 ± 0.002, 1.020 ± 0.003, 1.061 ± 0.003, 1.139 ± 0.005, and 1.022 ± 0.005, respectively. A computer-generated model, based on density functional electronic structure calculations, was fit to the experimental isotope effect. The structure of the transition state confirms that human Thymidine Phosphorylase proceeds ...