Catalyzes the hydrolysis of 10-formyltetrahydrofolate (formyl-FH4) to formate and tetrahydrofolate (FH4). Provides the major source of formate for the PurT-dependent synthesis of 5'-phosphoribosyl-N-formylglycinamide (FGAR) during aerobic growth. Has a role in regulating the one-carbon pool. (6S)-10-formyltetrahydrofolate + H2O = (6S)-5,6,7,8-tetrahydrofolate + formate + H(+) Activated by methionine, inhibited by glycine. Purine metabolism; IMP biosynthesis via de novo pathway; formate from 10-formyl-5,6,7,8-tetrahydrofolate: step 1/1. Homohexamer. Belongs to the PurU family.