Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.5.1.3 (dihydrofolate reductase)
5,819 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5-Formyltetrahydropteroylpolyglutamates can be synthesized and purified directly from dihydropteroylpolyglutamates in a single-step procedure without purification of intermediates and with yields greater than 90%. The procedure involves a coupled enzymatic synthesis of 10-formyltetrahydropteroylpolyglutamates using the enzymes dihydrofolate reductase, serine hydroxymethyltransferase, and C1-tetrahydrofolate synthase with catalytic amounts of NADPH. The 10-formyltetrahydropteroylpolyglutamates are subsequently converted to 5-formyltetrahydropteroylpolyglutamates at 90 degrees C with near quantitative yields. 5-Formyltetrahydropteroylpolyglutamates are the only stable reduced derivatives of tetrahydropteroylpolyglutamates and can be purified and stored indefinitely without decomposition. Additionally, 5-formyltetrahydropteroylpolyglutamates can be readily converted to other derivatives of tetrahydropteroylpolyglutamates with yields greater than 95%. Also described is the synthesis of tetrahydropteroylglutamates labeled at C-11 with either 14C or 13C. Rapid purification procedures for serine hydroxymethyltransferase and C1-tetrahydrofolate synthase from frozen rabbit livers are presented.
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PMID:Synthesis of (6S)-5-formyltetrahydropteroyl-polyglutamates and interconversion to other reduced pteroylpolyglutamate derivatives. 162 89

In order to determine the mechanism for the effects of homofolates on growth of Lactobacillus casei, polyglutamated derivatives of homofolate (HPteGlu), dihydrohomofolate and tetrahydrohomofolate (H4HPteGlu) were synthesized and tested as inhibitors of folate-requiring enzymes. The following L. casei enzymes were examined: thymidylate synthase (TS), glycinamide ribonucleotide formyltransferase (GARFT), aminoimidazolecarboxamide ribonucleotide formyltransferase, serine hydroxymethyltransferase and dihydrofolate reductase. Polyglutamates of (6R,S)-H4HPteGlu are potent inhibitors of TS and GARFT. For example, the IC50 values of (6R,S)-H4HPteGlu6 are 0.7 microM for TS and 0.3 microM for GARFT. By contrast, the value for HPteGlu6 is greater than 10 microM for both TS and GARFT. Inhibition of TS and GARFT by (6R,S)-H4HPteGlu derivatives increases with polyglutamate chain length. For TS, the Glu5 and Glu6 derivatives of (6R,S)-H4HPteGlu are 20 and 30 times more potent than the monoglutamate, respectively. For GARFT, the Glu2-6 derivatives are 2-3 times more potent than Glu1. Inhibition of TS and GARFT by (6R,S)-H4HPteGlu polyglutamates is almost entirely due to the unnatural (6R) diastereomer at C-6. Homofolate derivatives are only weak inhibitors of aminoimidazolecarboxamide ribonucleotide formyltransferase, serine hydroxymethyltransferase, and dihydrofolate reductase. We conclude that both TS and GARFT are potential targets of (6R)-H4HPteGlu polyglutamates.
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PMID:Tetrahydrohomofolate polyglutamates as inhibitors of thymidylate synthase and glycinamide ribonucleotide formyltransferase in Lactobacillus casei. 210 31

Serine hydroxymethyltransferase and the trifunctional enzyme C1-tetrahydrofolate synthase have been purified to near homogeneity from L1210 cells. Kinetic constants (Km and kcat) have been determined for both folate and non-folate substrates. The effect of increasing glutamate chain length on affinity and catalytic efficiency were determined for the four activities. The studies show that the structural and catalytic properties of the two L1210 enzymes are very similar to the corresponding enzymes purified from rabbit liver. Antibodies to both rabbit serine hydroxymethyltransferase and C1-tetrahydrofolate synthase cross-react with the corresponding L1210 enzymes. The intracellular concentration of active sites of serine hydroxymethyltransferase and C1-tetrahydrofolate synthase in L1210 cells are both 9 microM. The combined concentration of these two enzymes exceeds the previously reported concentration of 10 microM for total intracellular folates. A network thermodynamic computer model of one carbon metabolism (Seither, R. L., Trent, D. F., Mikulecky, D. C., Rape, T. J., and Goldman, I. D. (1989) J. Biol. Chem. 264, 17016-17023) suggests that complete inhibition of cytosolic serine hydroxymethyltransferase would neither significantly decrease the rates of biosynthesis of purines and thymidylate nor significantly alter the rate of interconversion of tetrahydrofolate cofactors to dihydrofolate with subsequent inhibition of dihydrofolate reductase.
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PMID:Purification and properties of serine hydroxymethyltransferase and C1-tetrahydrofolate synthase from L1210 cells. 237 84

Serine hydroxymethyltransferase (EC 2.1.2.1) was partially purified from a pyrimethamine sensitive strain of Plasmodium chabaudi. Km values of 2.91 and 1.08 mM were determined for tetrahydrofolate and serine, respectively. The effects of pH, of temperature and of some potential inhibitors were determined. The enzyme was also partially purified from a pyrimethamine-resistant strain of P. chabaudi and subjected to the same regime. No differences between the enzymes from the two sources could be detected. It would appear that the changes in properties in the enzymes dihydrofolate reductase and thymidylate synthetase associated with the development of drug resistance in P. chabaudi were not reflected in any obvious alterations in serine hydroxymethyltransferase.
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PMID:Serine hydroxymethyltransferase from pyrimethamine-sensitive and -resistant strains of Plasmodium chabaudi. 249 46

Folic acid metabolism in eukaryotic cells consists of a network of enzymatic reactions in which 1-carbon (C1) units at three different oxidation states are 1) interconverted while linked to the 5- and/or 10-positions of tetrahydrofolate, or 2) added to, or taken from, tetrahydrofolate. Particularly important in the latter category are reactions involving C1-tetrahydrofolate adducts in the synthesis of inosinate, thymidylate, serine, and methionine. Tetrahydrofolate, a central component of the network, can be generated from: 1) folate, via the NADPH-dependent dihydrofolate reductase; 2) 5-methyltetrahydrofolate via the methyl B12-dependent methionine synthetase; or 3) 5-formyltetrahydrofolate via a sequence of reactions beginning with the ATP-dependent isomerization to 5,10-methenyltetrahydrofolate or via transfer of the formyl group to glutamate. Because of the close relationship of folic acid metabolism to cell replication, folate-dependent enzymes provide excellent targets for cancer chemotherapy. This potential has not yet been realized, however, except for dihydrofolate reductase and thymidylate synthetase, which are strongly inhibited by the anti-cancer agents methotrexate (MTX) and FUra. The following enzymes are particularly attractive as targets for future exploitation in chemotherapy: 1) the two transformylases involved in purine nucleotide synthesis, 2) serine hydroxymethyltransferase, 3) methionine synthetase, and 4) methylenetetrahydrofolate dehydrogenase. Suggestions are also made for the development of new agents based upon a strategy of enzyme-targeted chemotherapy.
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PMID:Folic acid metabolism and its disruption by pharmacologic agents. 312 3

The use and metabolism of folates by leishmanias have been studied by assessing the growth of promastigotes in defined media with different folates and the cell content of folate-metabolising enzymes. The folates present in Leishmania mexicana mexicana have been determined using HPLC. Folic acid, 5-formyltetrahydrofolate (THF) and 5-methyl-THF each supported growth of L. m. mexicana promastigotes in defined medium, whereas the parasites did not survive in the absence of folates; p-aminobenzoic acid could not replace the folate requirement. The only folate present at detectable levels in L. m. mexicana promastigotes was 5-methyl-THF. Dihydrofolate reductase (EC 1.5.1.3), methylene-THF reductase (EC 1.1.1.68), serine hydroxymethyltransferase (EC 2.1.2.1) and thymidylate synthetase (EC 2.1.1.45) were all detected in extracts of promastigotes of L. m. mexicana, L. donovani and L. major. Some of these activities were also found in extracts of amastigotes of the former two species. The enzymes of L. m. mexicana have been partially characterised. Methylene-THF reductase may be involved in the conversion in vivo of 5-methyl-THF to 5,10-methylene-THF.
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PMID:Folate utilisation by Leishmania species and the identification of intracellular derivatives and folate-metabolising enzymes. 357 56

1. The specific activities of some enzymes of folate metabolism were measured in the liver of folate-treated and folate-deficient immature female chickens at intervals up to 9 days after an initial administration of 17 beta-oestradiol dipropionate. 2. An increase in dihydrofolate reductase activity after 3 days and decreases in 10-formyltetrahydrofolate synthetase and 5,10-methylenetetrahydrofolate dehydrogenase activities after 2 days became evident as a result of oestradiol treatment. 3. After 9 days, oestradiol caused a small decrease in glutamate formiminotransferase activity. 4. In folate-deficient chickens the activity of dihydrofolate reductase was decreased and that of serine hydroxymethyltransferase, 10-formyltetrahydrofolate synthetase and 5,10-methylenetetrahydrofolate dehydrogenase was increased in both non-hormone-treated and oestradiol-treated animals.
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PMID:Time-course studies on the effects of oestradiol administration on the activity of some folate-metabolizing enzymes in chicken liver. 706 1

In C3 plants large amounts of photorespiratory glycine (Gly) are converted to serine by the tetrahydrofolate (THF)-dependent activities of the Gly decarboxylase complex (GDC) and serine hydroxymethyltransferase (SHMT). Using 13C nuclear magnetic resonance, we monitored the flux of carbon through the GDC/SHMT enzyme system in Arabidopsis thaliana (L.) Heynh. Columbia exposed to inhibitors of THF-synthesizing enzymes. Plants exposed for 96 h to sulfanilamide, a dihydropteroate synthase inhibitor, showed little reduction in flux through GDC/SHMT. Two other sulfonamide analogs were tested with similar results, although all three analogs competitively inhibited the partially purified enzyme. However, methotrexate or aminopterin, which are confirmed inhibitors of Arabidopsis dihydrofolate reductase, decreased the flux through the GDC/SHMT system by 60% after 48 h and by 100% in 96 h. The uptake of [alpha-13C]Gly was not inhibited by either drug class. The specificity of methotrexate action was shown by the ability of 5-formyl-THF to restore flux through the GDC/SHMT pathway in methotrexate-inhibited plants. The experiments with sulfonamides strongly suggest that the mitochondrial THF pool has a long half-life. The studies with methotrexate support the additional, critical role of dihydrofolate reductase in recycling THF oxidized in thymidylate synthesis.
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PMID:Effects of sulfanilamide and methotrexate on 13C fluxes through the glycine decarboxylase/serine hydroxymethyltransferase enzyme system in arabidopsis. 944 40

Chemotherapeutic drugs targeted at folate-dependent reactions have typically been directed at a limited number of target enzymes: dihydrofolate reductase, thymidylate synthase, and GAR and AICAR transformylase. This review discusses two other potential targets for chemotherapeutic inhibition: cobalamin-dependent methionine synthase and serine hydroxymethyltransferase. Brief reviews of the catalytic properties of these two enzymes are presented, and possible strategies for chemotherapeutic intervention are discussed.
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PMID:Cobalamin-dependent methionine synthase and serine hydroxymethyltransferase: targets for chemotherapeutic intervention? 976 64

The global emergence of drug-resistant malarial parasites necessitates identification and characterization of novel drug targets. Three reactions are involved in methylenetetrahydrofolate recycling: Thymidylate synthase (TS), dihydrofolate reductase (DHFR), and serine hydroxymethyltransferase (SHMT). Malarial bifunctional DHFR-TS is a well-studied, important target of established drugs such as pyrimethamine and cycloguanil. In sharp contrast, malarial SHMT remains largely uncharacterized. In the present study, a Plasmodium falciparum SHMT coding region was characterized. It had 1603 bp including two introns near the 5'-end of the gene: one 118 bp intron immediately after the start methionine and a 159 bp intron after an additional 34 amino acids. The three exons together coded for a 442 amino acid protein with 38-47% identity to SHMT sequences from other species. Expression of malarial SHMT coding sequence (minus the introns) into glyA mutants of Escherichia coli relieved glycine auxotrophy and permitted direct assay of SHMT catalytic activity in bacterial cell lysates. This is the first SHMT cloned and expressed from a protozoan parasite. The molecular tools developed in this study will be useful for developing potential antimalarials directed at SHMT.
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PMID:Gene organization of a Plasmodium falciparum serine hydroxymethyltransferase and its functional expression in Escherichia coli. 1107 Dec 83


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