User:Cboursnell/Sandbox/5-FTHF cyc-lig

5-formyltetrahydrofolate cyclo-ligase or methenyl-THF synthetase EC catalyses the interchange of 5-formyltetrahydrofolate (5-FTHF) to 5-10-methenyltetrahydrofolate, this requires ATP and Mg2+. 5-FTHF is used in chemotherapy where it is clinically known as Leucovorin.