Inhibition of mammalian thymidylate synthase by 10-formyltetrahydropteroylpolyglutamate.
Reduced derivatives of 10-formylfolate have been evaluated as inhibitors of mammalian thymidylate synthase (EC 2.1.1.45) from H35 hepatoma cells. With 5,10-methylenetetrahydrofolylheptaglutamate as the substrate, 10-formyltetrahydrofolylmonoglutamate is a competitive inhibitor with a Ki of 2.4 microM, which is reduced to 0.1 microM for the heptaglutamate derivative. 10-Formyldihydrofolylmono- and -heptaglutamate are approximately threefold less inhibitory than the tetrahydro analog. The concentrations of 10-formyltetrahydrofolate and 10-formyldihydrofolate were measured in dividing hepatoma cells by a novel enzymatic assay and were found to be 5 microM and undetectable, respectively. These results suggest that the concentration of 10-formyltetrahydrofolate within the dividing cells has the potential to severely inhibit or modulate thymidylate biosynthesis.
Balinska
M
M
Wadsworth Center for Laboratories and Research, New York State Department of Health, Albany 12201-0509.
Rhee
M
M
Whiteley
J M
JM
Priest
D G
DG
Galivan
J
J
D000818:Animals; D001667:Binding, Competitive; D005575:Formyltetrahydrofolates / Q000494:pharmacology*; D005971:Glutamates / Q000494:pharmacology; D066298:In Vitro Techniques; D007700:Kinetics; D002955:Leucovorin / Q000031:analogs & derivatives / Q000378:metabolism; D008114:Liver Neoplasms, Experimental / Q000201:enzymology; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured
D005575:Formyltetrahydrofolates; D005971:Glutamates; C010161:10-formyltetrahydropteroylglutamic acid; D013940:Thymidylate Synthase; D002955:Leucovorin