Thymidylate synthase–fluorodeoxyuridylate–folate complex (TS–FdUMP complex)

The TS–FdUMP complex is a covalent ternary adduct formed when fluorodeoxyuridylate (FdUMP), an active metabolite of anti-cancer drugs like 5-fluorouracil, binds irreversibly to thymidylate synthase (TS) in the presence of folate cofactor[1][7][8]. This enzymatic inhibition disrupts DNA synthesis by depleting deoxythymidine monophosphate (dTMP), causing cytotoxicity in proliferating cells and forming the molecular basis for the use of fluoropyrimidine drugs in cancer chemotherapy[1][2][3][7]. While not a receptor or endogenous molecule per se, this complex is fundamental for drug efficacy and is studied both as a pharmacodynamic marker and for biomarker development[6]. The formation of this complex constitutes a classical example of suicide inhibition and is characterized structurally by covalent bonds involving the enzyme, inhibitor, and cofactor, leading to irreversible inactivation of TS[3][5][7].

Other names

Thymidylate synthase–FdUMP complexTS–FdUMP–folate ternary complexCovalent TS–FdUMP complex5FU-modified TS

Suicide inhibition: FdUMP, derived from 5-FU metabolism, binds irreversibly to TS in the presence of folate cofactor, creating a covalent ternary complex that blocks dTMP synthesis, leading to DNA synthesis inhibition and cell death. Competitive inhibition: Certain antifolates displace natural substrate and bind within the active site, preventing catalysis.