This gene encodes a trifunctional cytoplasmic enzyme. The encoded protein functions as a methylenetetrahydrofolate dehydrogenase, a methenyltetrahydrofolate cyclohydrolase, and a formyltetrahydrofolate synthase. The encoded enzyme functions in de novo synthesis of purines and thymidylate and in regeneration of methionine from homocysteine. [provided by RefSeq, Oct 2009]