MTHFS is a cytosolic protein which takes part in the formate metabolic process. MTHFS along with a magnesium cofactor catalyzes the ATP-dependent reaction which reduces 5-formyltetrahydrofolate(5-MTHF) to 5,10-methenyltetrahydrofolate(MTHF). MTHF is the substrate used by MTHFR(methylenetetrahydrofolate reductase) to generate 5-MTHF. In addition, MTHF is a coenzyme used in thymidine biosynthesis by thymidylate synthase(FAD).