Pteroylpolyglutamates

Kisliuk, Roy L.

doi:10.1007/978-94-009-8027-3_21

Cited by 2 publications

(3 citation statements)

References 107 publications

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“…The first-order rate constant k 3 was estimated based on the thymidylate synthase (TS) flux known to be required to support DNA replication, and on the assumption that 5,10-methylene- H 4 PteGlu 3 (the most abundant and preferred folate substrate32) is the primary folate feeding this reaction (flux TS ≈ k 3 × pool size (C1)-H4PteGlu3 ). The experimentally observed ratio of DHF triglutamate to all reduced triglutamate species was then used to determine k 4 based on the steady state assumption ( k 3 × pool size (C1)-H4PteGlu3 ≈ k 4 × pool size H2PteGlu3 ).…”

Section: Resultsmentioning

confidence: 99%

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A domino effect in antifolate drug action in Escherichia coli

et al. 2008

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Mass spectrometry technologies for measurement of cellular metabolism are opening new avenues to explore drug activity. Trimethoprim is an antibiotic that inhibits bacterial dihydrofolate reductase (DHFR). Kinetic flux profiling with 15 N-labeled ammonia in Escherichia coli reveals that trimethoprim leads to blockade not only of DHFR but also of another critical enzyme of folate metabolism: folylpoly-γ-glutamate synthetase (FP-γ-GS). Inhibition of FP-γ-GS is not directly due to trimethoprim. Instead, it arises from accumulation of DHFR's substrate dihydrofolate, which we show is a potent FP-γ-GS inhibitor. Thus, owing to the inherent connectivity of the metabolic network, falling DHFR activity leads to falling FP-γ-GS activity in a domino-like cascade. This cascade results in complex folate dynamics, and its incorporation in a computational model of folate metabolism recapitulates the dynamics observed experimentally. These results highlight the potential for quantitative analysis of cellular metabolism to reveal mechanisms of drug action.Enzyme inhibition is among the best established mechanisms of drug action 1 . Nevertheless, even for enzyme inhibitors, the mechanisms of action are often incompletely understood 2 . For example, drugs known to be inhibitors of one enzyme may further bind to unidentified enzymes or indirectly interact with other pathways. In part, this limited understanding is due to the scope and complexity of cellular chemical reactions as well as the associated difficulty of tracking many reactions at once. The recent development of technologies that can measure many cellular metabolites 3-5 and metabolic fluxes 6-8 in parallel may allow for more complete elucidation of actions of enzyme inhibitors. Here we apply LC-MS/MS to explore the effects of the DHFR inhibitor trimethoprim (1) in Escherichia coli by tracking both metabolite concentrations and fluxes throughout the folate pathway.Folates are cofactors that accept or donate one-carbon units for the biosynthesis of essential metabolites including purines, thymine (2), methionine (3) and glycine (4). Folate metabolism is the target of many therapeutics, including antibiotics (trimethoprim and sulfa drugs) 9-11 and anticancer agents (methotrexate, 5, and pemetrexed, 6) 12 . Folates are synthesized from GTP (7), p-aminobenzoic acid (pABA, 8) and glutamates (9) and can exist in three different oxidation/reduction states: PteGlu n (pteroylglutamate, or folate,

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Section: Resultsmentioning

confidence: 99%

“…It yields k 3 > k 2 > k 1 , which is consistent with the biochemically observed preference of TS for 5,10-methylene-H 4 PteGlu 3 (ref. 32). Experimental determination of the flux from triglutamates to tetraglutamates via FP-α-GS was used to determine k 6 (flux FP-α-GS ≈ k 6 × pool size (C1)-H4PteGlu3 ).…”

Section: Resultsmentioning

confidence: 99%

A domino effect in antifolate drug action in Escherichia coli

et al. 2008

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“…It has been proposed that the tight binding of folylpolyglutamates increases the efficiency of sequential folate‐dependent proteins by enhancing the channelling of intermediates between the active sites 39. 66, 72 Supporting this view, it has been shown with formiminotransferase‐cyclodeaminase73 that the specificity for channelling was optimal for H 4 FGlu 5 , the pentaglutamate derivatives being one of the predominant polyglutamate forms of folate in animals74 and plants 67. 69 Another example of folate channelling between two catalytic domains is shown with the bifunctional DHFR/TS.…”

Section: Biosynthesismentioning

confidence: 99%

Folic acid and folates: the feasibility for nutritional enhancement in plant foods

Scott¹,

Rébeillé²,

Fletcher³

2000

J. Sci. Food Agric.

289

237

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In mammalian and plant cells the folates play a key role in the methylation cycle and in the DNA biosynthesis cycle (in the de novo biosynthesis of purines and pyrimidines). Deficiency of folate in the diet is likely to result in a reduction in the capacity to synthesise DNA and maintain the usual rate of cell division. This most evidently results in the production of anaemia from folate deficiency due to a reduction in the biosynthesis of cells in the bone marrow. In addition it has been shown that high levels of plasma homocysteine occur which is an important risk factor in cardiovascular disease. Furthermore it has been shown that reduced maternal folate status is associated with the progressive increase in neural tube defects in infants. There is good evidence for folate deficiency in a considerable number of the population in developed countries, even where folate supplementation of foods is practised, and for a level of intake in excess of the recommended dietary allowance. This paper reviews the principal routes of folate biosynthesis in plants and the potential for increasing the levels of natural folates through conventional plant breeding and biotechnological means. The effect of the major food preservation processes on the levels of folates in plants is also reviewed. The current information about the bioavailability of folates from plant food sources, and how this might be improved, is also summarised. The important health benefits that would arise from increasing folate intake in the diet provide a strong incentive for considering how this might be achieved. © 2000 Society of Chemical Industry

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Pteroylpolyglutamates

Cited by 2 publications

References 107 publications

A domino effect in antifolate drug action in Escherichia coli

A domino effect in antifolate drug action in Escherichia coli

Folic acid and folates: the feasibility for nutritional enhancement in plant foods

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