Involved in the removal of 5-formyltetrahydrofolate. In vitro, it is a potent inhibitor of various folate-dependent enzymes in the C1 metabolism network and in vivo it might function as a folate storage. 5-formyltetrahydrofolate is also used as an antifolate rescue agent in cancer chemotherapy. Catalyzes the irreversible ATP-dependent transformation of 5-formyltetrahydrofolate (5-CHO-THF) to form 5,10-methenyltetrahydrofolate (5,10-CH=THF). The reverse reaction is catalyzed by the serine hydroxymethyltransferase GlyA (SHMT) 