5-formyltetrahydrofolate cyclo-ligase (MTHFS) belongs to the 5-formyltetrahydrofolate cyclo-ligase family. It is an enzyme that catalyzes the conversion of 5-formyltetrahydrofolate to 5,10-methenyltetrahydrofolate, contributes to tetrahydrofolate metabolism. MTHFS helps regulate carbon flow through the folate-dependent one-carbon metabolic network that supplies carbon for the biosynthesis of purines, thymidine and amino acids. An increased activity of the encoded protein can result in an increased folate turnover rate and folate depletion.