IUBMB Enzyme Nomenclature


Accepted name: methenyltetrahydrofolate cyclohydrolase

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 and formate—tetrahydrofolate ligase (EC activity. In some prokaryotes, it occurs as a bifunctional enzyme that also has dehydrogenase (EC activity or formimidoyltetrahydrofolate cyclodeaminase (EC activity.

Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9027-97-8


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.

[EC created 1961]

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