Serine hydroxymethyltransferase

Catalyzes the reversible interconversion of serine and glycine with tetrahydrofolate (THF) serving as the one-carbon carrier. This reaction serves as the major source of one-carbon groups required for the biosynthesis of purines, thymidylate, methionine, and other important biomolecules. Also exhibits THF-independent aldolase activity toward beta-hydroxyamino acids, producing glycine and aldehydes, via a retro-aldol mechanism. Thus, is able to catalyze the cleavage of allothreonine and 3-phenylserine. Also catalyzes the irreversible conversion of 5,10-methenyltetrahydrofolate to 5-formyltetrahydrofolate.