Enzyme inhibitors, such as FdUMP, that inactivate an enzyme only after undergoing part or all of the normal catalytic reaction are cat mechanism-based inhibitors (alternatively, suicide substrates because they cause the enzyme to "commit suicide"). Because of their extremely high specificity, mechanism-based inhibitors are among the most useful therapeutic agents.
Inhibiton of DHFR blocks dTMP synthesis as well as all other THF-dependent biological reactions, because the THF converted to DHF by the thymidylate synthase reaction cannot be regenerated Methotrexate (amethopterin), aminopterin, and thrimethoprim