Tetrahydrofolate

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Henk J Blom - One of the best experts on this subject based on the ideXlab platform.

  • decreased methylene Tetrahydrofolate reductase activity due to the 677c t mutation in families with spina bifida offspring
    Journal of Molecular Medicine, 1996
    Co-Authors: L P W J Van Den Heuvel, Regine P M Steegerstheunissen, F J M Trijbels, T K A B Eskes, Edwin C M Mariman, Den M Heyer, Henk J Blom
    Abstract:

    Periconceptional folate intake reduces both the occurrence and recurrence risk of neural tube defects. Plasma homocysteine levels can be elevated in mothers of a child with a neural tube defect, suggesting a dysfunctional folate metabolism. Very recently we showed that a common 677C→T mutation in the 5,10-methylene Tetrahydrofolate reductase gene, causing thermolability of the enzyme, is a risk factor for spina bifida offspring. Restriction enzyme analysis of the genomic 5,10-methylene Tetrahydrofolate reductase polymerase chain reaction fragment revealed a significantly higher prevalence of a +/+ genotype among spina bifida patients and their mothers. The risk for spina bifida offspring is the strongest if both the mother and her child have the mutation in the homozygous state. Enzymatic analysis showed that homozygosity for the 677C→T mutation causes a decreased 5,10-methylene Tetrahydrofolate reductase activity, resulting in elevated plasma homocysteine and red blood cell folate levels and lowered plasma folate and cysteine values. This extended study demonstrates that a nucleotide substitution in the coding region of 5,10-methylene Tetrahydrofolate reductase, resulting in reduced activity and an impaired homocysteine and folate metabolism, is a genetic risk factor for spina bifida.

  • Decreased methylene Tetrahydrofolate reductase activity due to the 677C→T mutation in families with spina bifida offspring
    Journal of Molecular Medicine, 1996
    Co-Authors: L P W J Van Den Heuvel, F J M Trijbels, T K A B Eskes, Edwin C M Mariman, Régine P.m. Steegers-theunissen, M. Den Heyer, Henk J Blom
    Abstract:

    Periconceptional folate intake reduces both the occurrence and recurrence risk of neural tube defects. Plasma homocysteine levels can be elevated in mothers of a child with a neural tube defect, suggesting a dysfunctional folate metabolism. Very recently we showed that a common 677C→T mutation in the 5,10-methylene Tetrahydrofolate reductase gene, causing thermolability of the enzyme, is a risk factor for spina bifida offspring. Restriction enzyme analysis of the genomic 5,10-methylene Tetrahydrofolate reductase polymerase chain reaction fragment revealed a significantly higher prevalence of a +/+ genotype among spina bifida patients and their mothers. The risk for spina bifida offspring is the strongest if both the mother and her child have the mutation in the homozygous state. Enzymatic analysis showed that homozygosity for the 677C→T mutation causes a decreased 5,10-methylene Tetrahydrofolate reductase activity, resulting in elevated plasma homocysteine and red blood cell folate levels and lowered plasma folate and cysteine values. This extended study demonstrates that a nucleotide substitution in the coding region of 5,10-methylene Tetrahydrofolate reductase, resulting in reduced activity and an impaired homocysteine and folate metabolism, is a genetic risk factor for spina bifida.

Stephen M. Beverley - One of the best experts on this subject based on the ideXlab platform.

  • The enzymes of the 10-formyl-Tetrahydrofolate synthetic pathway are found exclusively in the cytosol of the trypanosomatid parasite Leishmania major
    Molecular and Biochemical Parasitology, 2009
    Co-Authors: Tim J. Vickers, Silvane M. F. Murta, Michael A. Mandell, Stephen M. Beverley
    Abstract:

    In most organisms 10-formyl-Tetrahydrofolate (10-CHO-THF) participates in the synthesis of purines in the cytosol and formylation of mitochondrial initiator methionyl-tRNAMet. Here we studied 10-CHO-THF biosynthesis in the protozoan parasite Leishmania major, a purine auxotroph. Two distinct synthetic enzymes are known, a bifunctional methylene-Tetrahydrofolate dehydrogenase/cyclohydrolase (DHCH) or formyl-Tetrahydrofolate ligase (FTL), and phylogenomic profiling revealed considerable diversity for these in trypanosomatids. All species surveyed contain a DHCH1, which was shown recently to be essential in L. major. A second DHCH2 occurred only in L. infantum, L. mexicana and T. cruzi, and as a pseudogene in L. major. DHCH2s bear N-terminal extensions and we showed a LiDHCH2-GFP fusion was targeted to the mitochondrion. FTLs were found in all species except Trypanosoma brucei. L. major ftl− null mutants were phenotypically normal in growth, differentiation, animal infectivity and sensitivity to a panel of pteridine analogs, but grew more slowly when starved for serine or glycine, as expected for amino acids that are substrates in C1-folate metabolism. Cell fractionation and western blotting showed that both L. major DHCH1 and FTL were localized to the cytosol and not the mitochondrion. These localization data predict that in L. major cytosolic 10-formyl-Tetrahydrofolate must be transported into the mitochondrion to support methionyl-tRNAMet formylation. The retention in all the trypanosomatids of at least one enzyme involved in 10-formyl-Tetrahydrofolate biosynthesis, and the essentiality of this metabolite in L. major, suggests that this pathway represents a promising new area for chemotherapeutic attack in these parasites.

  • methylene Tetrahydrofolate dehydrogenase cyclohydrolase and the synthesis of 10 cho thf are essential in leishmania major
    Molecular Microbiology, 2009
    Co-Authors: Silvane M. F. Murta, Tim J. Vickers, David A Scott, Stephen M. Beverley
    Abstract:

    Summary 10-Formyl Tetrahydrofolate (10-CHO-THF) is a key metabolite in C1 carbon metabolism, arising through the action of formate-Tetrahydrofolate ligase (FTL) and/or 5,10-methenylTetrahydrofolate cyclohydrolase/ 5,10-methylene Tetrahydrofolate dehydrogenase (DHCH). Leishmania major possesses single DHCH1 and FTL genes encoding exclusively cytosolic pro- teins, unlike other organisms where isoforms occur in the mitochondrion as well. Recombinant DHCH1 showed typical NADP + -dependent methylene tetrahy- drofolate DH and 5,10-methenylTetrahydrofolate CH activities, and the DH activity was potently inhibited by a substrate analogue 5,10-CO-THF (Ki 105 nM), as was Leishmania growth (EC50 1.1 mM). Previous studies showed null ftl - mutants were normal, raising the possibility that loss of the purine synthetic pathway had rendered 10-CHO-THF dispensable in evolution. We were unable to generate dhch1 - null mutants by gene replacement, despite using a wide spectrum of nutritional supplements expected to bypass DHCH function. We applied an improved method for testing essential genes in Leishmania, based on segregational loss of episomal comple- menting genes rather than transfection; analysis of ~1400 events without successful loss of DHCH1 again established its requirement. Lastly, we employed 'genetic metabolite complementation' using ectopi- cally expressed FTL as an alternative source of 10-CHO-THF; now dhch1 - null parasites were readily obtained. These data establish a requirement for 10-CHO-THF metabolism in L. major, and provide genetic and pharmacological validation of DHCH as a target for chemotherapy, in this and potentially other protozoan parasites.

Lujun Gu - One of the best experts on this subject based on the ideXlab platform.

L P W J Van Den Heuvel - One of the best experts on this subject based on the ideXlab platform.

  • decreased methylene Tetrahydrofolate reductase activity due to the 677c t mutation in families with spina bifida offspring
    Journal of Molecular Medicine, 1996
    Co-Authors: L P W J Van Den Heuvel, Regine P M Steegerstheunissen, F J M Trijbels, T K A B Eskes, Edwin C M Mariman, Den M Heyer, Henk J Blom
    Abstract:

    Periconceptional folate intake reduces both the occurrence and recurrence risk of neural tube defects. Plasma homocysteine levels can be elevated in mothers of a child with a neural tube defect, suggesting a dysfunctional folate metabolism. Very recently we showed that a common 677C→T mutation in the 5,10-methylene Tetrahydrofolate reductase gene, causing thermolability of the enzyme, is a risk factor for spina bifida offspring. Restriction enzyme analysis of the genomic 5,10-methylene Tetrahydrofolate reductase polymerase chain reaction fragment revealed a significantly higher prevalence of a +/+ genotype among spina bifida patients and their mothers. The risk for spina bifida offspring is the strongest if both the mother and her child have the mutation in the homozygous state. Enzymatic analysis showed that homozygosity for the 677C→T mutation causes a decreased 5,10-methylene Tetrahydrofolate reductase activity, resulting in elevated plasma homocysteine and red blood cell folate levels and lowered plasma folate and cysteine values. This extended study demonstrates that a nucleotide substitution in the coding region of 5,10-methylene Tetrahydrofolate reductase, resulting in reduced activity and an impaired homocysteine and folate metabolism, is a genetic risk factor for spina bifida.

  • Decreased methylene Tetrahydrofolate reductase activity due to the 677C→T mutation in families with spina bifida offspring
    Journal of Molecular Medicine, 1996
    Co-Authors: L P W J Van Den Heuvel, F J M Trijbels, T K A B Eskes, Edwin C M Mariman, Régine P.m. Steegers-theunissen, M. Den Heyer, Henk J Blom
    Abstract:

    Periconceptional folate intake reduces both the occurrence and recurrence risk of neural tube defects. Plasma homocysteine levels can be elevated in mothers of a child with a neural tube defect, suggesting a dysfunctional folate metabolism. Very recently we showed that a common 677C→T mutation in the 5,10-methylene Tetrahydrofolate reductase gene, causing thermolability of the enzyme, is a risk factor for spina bifida offspring. Restriction enzyme analysis of the genomic 5,10-methylene Tetrahydrofolate reductase polymerase chain reaction fragment revealed a significantly higher prevalence of a +/+ genotype among spina bifida patients and their mothers. The risk for spina bifida offspring is the strongest if both the mother and her child have the mutation in the homozygous state. Enzymatic analysis showed that homozygosity for the 677C→T mutation causes a decreased 5,10-methylene Tetrahydrofolate reductase activity, resulting in elevated plasma homocysteine and red blood cell folate levels and lowered plasma folate and cysteine values. This extended study demonstrates that a nucleotide substitution in the coding region of 5,10-methylene Tetrahydrofolate reductase, resulting in reduced activity and an impaired homocysteine and folate metabolism, is a genetic risk factor for spina bifida.

Fabrice Rébeillé - One of the best experts on this subject based on the ideXlab platform.

  • The Uniqueness of Tetrahydrofolate Synthesis and One-Carbon Metabolism in Plants
    Plant Mitochondria: From Genome to Function, 2020
    Co-Authors: Stephane Ravanel, Roland Douce, Fabrice Rébeillé
    Abstract:

    In all living organisms a great variety of reactions involve transfer of single carbon units from one molecule to another. These one-carbon (C1) reactions play essential roles in major cellular processes including the synthesis of nucleic acids, protein biosynthesis in the organelles, amino acid metabolism, pantothenate biosynthesis, and the biogenesis of many methylated products. One-carbon transfer reactions are mediated by Tetrahydrofolate, a soluble coenzyme (vitamin B9) that is synthesized de novo by plants and microorganisms, and absorbed from the diet by animals. C1 metabolism and Tetrahydrofolate synthesis in plants exhibit features that are not found in other organisms. Beyond the unique gene organization and/or biochemical properties of some of these reactions, the most fascinating aspect is the complex subcellular compartmentation of folate synthesis and folate-mediated reactions in the plant cell. Thus, the enzymes involved in the biogenesis of Tetrahydrofolate are distributed over the plastids, the cytosol, and the mitochondria. Also, these compartments contain parallel sets of activities required to generate C1-substituted folate coenzymes. This chapter will focus on the most recent advances in knowledge of C1 metabolism in plants with particular emphasize regardir the role of mitochondria and the traffic of folate coenzymes between the different compartments.

  • Tetrahydrofolate biosynthesis in plants molecular and functional characterization of dihydrofolate synthetase and three isoforms of folylpolyglutamate synthetase in arabidopsis thaliana
    Proceedings of the National Academy of Sciences of the United States of America, 2001
    Co-Authors: Stephane Ravanel, Roland Douce, H Cherest, Samuel Jabrin, Didier Grunwald, Yolande Surdinkerjan, Fabrice Rébeillé
    Abstract:

    Tetrahydrofolate coenzymes involved in one-carbon (C1) metabolism are polyglutamylated. In organisms that synthesize Tetrahydrofolate de novo, dihydrofolate synthetase (DHFS) and folylpolyglutamate synthetase (FPGS) catalyze the attachment of glutamate residues to the folate molecule. In this study we isolated cDNAs coding a DHFS and three isoforms of FPGS from Arabidopsis thaliana. The function of each enzyme was demonstrated by complementation of yeast mutants deficient in DHFS or FPGS activity, and by measuring in vitro glutamate incorporation into dihydrofolate or Tetrahydrofolate. DHFS is present exclusively in the mitochondria, making this compartment the sole site of synthesis of dihydrofolate in the plant cell. In contrast, FPGS is present as distinct isoforms in the mitochondria, the cytosol, and the chloroplast. Each isoform is encoded by a separate gene, a situation that is unique among eukaryotes. The compartmentation of FPGS isoforms is in agreement with the predominance of γ-glutamyl-conjugated Tetrahydrofolate derivatives and the presence of serine hydroxymethyltransferase and C1-Tetrahydrofolate interconverting enzymes in the cytosol, the mitochondria, and the plastids. Thus, the combination of FPGS with these folate-mediated reactions can supply each compartment with the polyglutamylated folate coenzymes required for the reactions of C1 metabolism. Also, the multicompartmentation of FPGS in the plant cell suggests that the transported forms of folate are unconjugated.

  • Interaction between glycine decarboxylase, serine hydroxymethyltransferase and Tetrahydrofolate polyglutamates in pea leaf mitochondria
    Biochemical Journal, 1994
    Co-Authors: Fabrice Rébeillé, Michel Neuburger, Roland Douce
    Abstract:

    The aim of the present work was to further determine how the T-protein of the glycine-cleavage system and serine hydroxy-methyltransferase (SHMT), two folate-dependent enzymes from pea leaf mitochondria, interact through a common pool of Tetrahydrofolate polyglutamates (H4PteGlun). It was observed that the binding affinity of Tetrahydrofolate polyglutamates for these proteins continuously increased with increasing number of glutamates up to six residues. It was also established that, once bound to the proteins, Tetrahydrofolate, a very O2-sensitive molecule, was protected from oxidative degradation. The dissociation constants (Kd) of H4PteGlu5, the most predominant form of polyglutamate in the mitochondria, were approximately 0.5 microM for both T-protein and SHMT, whereas the Kd values of CH2-H4PteGlu5 were higher, 2.7 and 7 microM respectively. In a matrix extract from pea leaf mitochondria, the maximal activity of the glycine-cleavage system was about 2.5 times higher than the maximal activity of SHMT. This resulted in a permanent disequilibrium of the SHMT-catalysed reaction which was therefore driven toward the production of serine and H4PteGlun, the thermodynamically unfavourable direction. Indeed, measurements of the steady-state ratio of CH2-H4PteGlun/H4PteGlun (n = 1 or n = 5) during the course of glycine oxidation demonstrated that the methylene form accounted for 65-80% of the folate pool. This indicates that, in our in vitro experiments, CH2-H4PteGlun with long polyglutamate chains accumulated in the bulk medium. This observation suggests that, in these in vitro experiments at least, there was no channelling of CH2-H4PteGlu5 between the T-protein and SHMT.

  • Effects of Tetrahydrofolate polyglutamates on the kinetic parameters of serine hydroxymethyltransferase and glycine decarboxylase from pea leaf mitochondria.
    Biochemical Journal, 1993
    Co-Authors: V. Besson, Fabrice Rébeillé, Michel Neuburger, Roland Douce, E. A. Cossins
    Abstract:

    Plant tissues contain highly conjugated forms of folate. Despite this, the ability of plant folate-dependent enzymes to utilize Tetrahydrofolate polyglutamates has not been examined in detail. In leaf mitochondria, the glycine-cleavage system and serine hydroxymethyltransferase, present in large amounts in the matrix space and involved in the photorespiratory cycle, necessitate the presence of Tetrahydrofolate as a cofactor. The aim of the present work was to determine whether glutamate chain length (one to six glutamate residues) influenced the affinity constant for Tetrahydrofolate and the maximal velocities displayed by these two enzymes. The results show that the affinity constant decreased by at least one order of magnitude when the Tetrahydrofolate substrate contained three or more glutamate residues. In contrast, maximal velocities were not altered in the presence of these substrates. These results are consistent with analyses of mitochondrial folates which revealed a pool of polyglutamates dominated by tetra and pentaglutamates. The equilibrium constant of the serine hydroxymethyltransferase suggests that, during photorespiration, the reaction must be permanently pushed toward the formation of serine (the unfavourable direction) to allow the recycling of Tetrahydrofolate necessary for the operation of the glycine decarboxylase T-protein.