Catalyzes the oxidation of 5,10- methylenetetrahydrofolate to 5,10-methenyltetrahydrofolate and then the hydrolysis of 5,10-methenyltetrahydrofolate to 10- formyltetrahydrofolate (By similarity). Methenyltetrahydrofolate cyclohydrolase 291 BLD_0746 Methylenetetrahydrofolate dehydrogenase Bifunctional protein FolD MSTKIDGKQIAAEIKTNLAERVNKLKAQGIQPGLGTLLVGEDPGSMKYVAGKHADCQEVGITSVKKELPADASFDDIAAAVRELNEDPACTGFIVQLPLPKGINENAIIDMIDPAKDADGMHPYNLGELVLHVRGDISTPLPCTPRGVLELLDAYDIDLNGKEVCVLGRGITIGRTIGLMLTRNAVNATVTLCHTGTRDVADHMRRADVIVAAMGSAGFVTPDKIKDGAVLVDVGVSRVYDEEAGRYRIKGDVDKACYDKASAYTPNPGGVGPMTRAMLLANVVEMAERHA FOLD_BIFLD folD