EC - Methenyltetrahydrofolate cyclohydrolase

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IntEnz Enzyme Nomenclature


Accepted name:
methenyltetrahydrofolate cyclohydrolase
Other names:
Citrovorum factor cyclodehydrase
formyl-methenyl-methylenetetrahydrofolate synthetase (combined)
5,10-methenyltetrahydrofolate 5-hydrolase (decyclizing)
Systematic name:
5,10-methenyltetrahydrofolate 5-hydrolase (ring-opening)



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 formiminotetrahydrofolate cyclodeaminase (EC activity.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , NIST 74 , UniPathway
Protein domains and families: PROSITE:PDOC00616
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004477
CAS Registry Number: 9027-97-8
UniProtKB/Swiss-Prot: (834) [show] [UniProt]


  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 : 4176-4178 (1956).
  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 : 1830-1846 (1959).

[EC created 1961]