Reaction: 5,10-methenyltetrahydrofolate + H2O = 10-formyltetrahydrofolate
For diagram of reaction click here (another example).
Other name(s): Citrovorum factor cyclodehydrase; cyclohydrolase; formyl-methenyl-methylenetetrahydrofolate synthetase (combined); 5,10-methenyltetrahydrofolate 5-hydrolase (decyclizing)
Systematic name: 5,10-methenyltetrahydrofolate 5-hydrolase (ring-opening)
Comments: In eukaryotes, the enzyme occurs as a trifunctional enzyme that also has methylenetetrahydrofolate dehydrogenase (NADP+) (EC 1.5.1.5) and formate—tetrahydrofolate ligase (EC 6.3.4.3) activity. In some prokaryotes, it occurs as a bifunctional enzyme that also has dehydrogenase (EC 1.5.1.5) activity or formimidoyltetrahydrofolate cyclodeaminase (EC 4.3.1.4) activity.
Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9027-97-8
References:
1. Rabinowitz, J.C. and Pricer, W.E. The enzymatic synthesis of N10-formyltetrahydrofolic acid and its role in ATP formation during formiminoglycine degradation. J. Am. Chem. Soc. 78 (1956) 4176-4178.
2. Tabor, H. and Wyngaarden, L. The enzymatic formation of formiminotetrahydrofolic acid, 5,10-methenyltetrahydrofolic acid, and 10-formyltetrahydrofolic acid in the metabolism of formiminoglutamic acid. J. Biol. Chem. 234 (1959) 1830-1846.