Figure 1. Mechanisms by which fluoropyrimidine compounds interfere with DNA/RNA synthesis. 5-FU, 5-Fluorouracil; OPRT, ortate phosphoribosyl transferase; FUMP, 5-fluorouridine monophosphate; FUTP, 5-fluorouridine triphosphate; TP, thymidine phosphorylase; FUdR, 5-fluorodeoxyuridine; FdUMP, 5-fluorodeoxyuridine monophosphate; FdUTP, 5-fluorodeoxyuridine triphosphate; TS, thymidine synthase; dUMP, deoxyuridine monophosphate; dTMP, deoxythymidine monophosphate; dTTP, deoxythymidien triphosphate; DPD, dehydropyrimidine dehydrogenase; DHFR, dehydropholate reductase; THF, tetrahydropholate; Me-THF, methyltetrapholate.