Figure 6.

Concentration–response curves of FdUMP (a) and active 5′-functionalized analogs (b and c) against recombinant hTS-mediated conversion of 2′-deoxyuridine monophosphate (dUMP) and 5,10-methylene tetrahydrofolate (mTHF) to deoxythymidine monophosphate (dTMP) and dihydrofolate (DHF), respectively. The final concentrations of hTS, dUMP, and mTHF in the reaction systems were 0.84 μM, 50 μM, and 250 μM, respectively. The reaction rates were determined by following the change in the optical absorbance at 340 nm, which corresponded to the formation of the coproduct, DHF.