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

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

Extensive biochemical and pharmacological evidence indicates that LY231514 is a novel antifolate antimetabolite. LY231514 is transported into cells mainly through the reduced folate carrier system and extensively metabolized to polyglutamated forms. The polyglutamates of LY231514 inhibit at least three key folate enzymes: TS, DHFR, and GARFT, and to a lesser extent AICARFT and C1-tetrahydrofolate synthase. The combined effects of the inhibition exerted by LY231514 at each target give rise to an unusual end-product reversal pattern at the cellular level that is distinct from those of other inhibitors such as methotrexate and the quinazoline antifolates. The metabolic effects exerted by LY231514 on the folate and nucleotide pools are also quite distinct from those of MTX and LY309887. The efficient polyglutamation, longer cellular retention and the multiple folate enzyme inhibition mechanism may all have contributed directly to the exciting antitumor responses now observed in Phase I and II studies. The multitargeted inhibition mechanism of LY231514 is particularly intriguing. This new level of mechanistic insight, which has evolved from the study of LY231514, challenges the traditional concept and paradigm of antifolate drug discovery and development which focused on developing very potent and selective inhibitors of single folate enzyme targets, such as DHFR, TS or one of the enzymes along the de novo purine biosynthetic pathway. Given the complex nature of folate metabolism and the critical role of folates in maintaining the physiological functions of living systems, it is completely reasonable to suspect that agents which can interfere at multiple sites in the folate pathway may trigger and cause more biochemical imbalance in the cellular DNA and RNA synthesis of malignant cells than agents that act on a single point (Fig. 5). In conclusion, LY231514 (MTA) is a new generation antifolate antimetabolite demonstrating inhibitory activity against multiple folate enzymes including TS, DHFR and GARFT. In current phase II studies, MTA is broadly active as a single agent and is showing very encouraging antitumor activity in multiple solid tumors including colorectal, breast and non-small cell lung cancers (38-43). The every three week dosing schedule has proven to be convenient and easy to administer and the clinical toxicities of LY231514 seem to be well tolerated. More advanced and extensive clinical trials of LY231514 are currently in progress.
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PMID:Multiple folate enzyme inhibition: mechanism of a novel pyrrolopyrimidine-based antifolate LY231514 (MTA). 976 51