Methenyltetrahydrofolate cyclohydrolase

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methenyltetrahydrofolate cyclohydrolase
Methenyltetrahydrofolate cyclohydrolase dimer, Human
EC no.
CAS no.9027-97-8
IntEnzIntEnz view
ExPASyNiceZyme view
MetaCycmetabolic pathway
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

In enzymology, a methenyltetrahydrofolate cyclohydrolase (EC is an enzyme that catalyzes the chemical reaction

5,10-methenyltetrahydrofolate + H2O 10-formyltetrahydrofolate

Thus, the two substrates of this enzyme are 5,10-methenyltetrahydrofolate and H2O, whereas its product is 10-formyltetrahydrofolate.

This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amidines.

This enzyme participates in glyoxylate and dicarboxylate metabolism and one carbon pool by folate.


The systematic name of this enzyme class is 5,10-methenyltetrahydrofolate 5-hydrolase (decyclizing).

Other names in common use include:

  • Citrovorum factor cyclodehydrase
  • cyclohydrolase
  • formyl-methenyl-methylenetetrahydrofolate synthetase (combined).

Structural studies[edit]

As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes 1A4I, 1DIA, 1DIB, 1DIG, 2C2X, and 2C2Y.


  • Rabinowitz JC, Pricer WE (1956). "The enzymatic synthesis of N10-formyltetrahydrofolic acid and its role in ATP formation during formiminoglycine degradation". J. Am. Chem. Soc. 78 (16): 4176–4178. doi:10.1021/ja01597a094.
  • Tabor H, Wyngarden L (July 1959). "The enzymatic formation of formiminotetrahydrofolic acid, 5,10-methenyltetrahydrofolic acid, and 10-formyltetrahydrofolic acid in the metabolism of formiminoglutamic acid". The Journal of Biological Chemistry. 234 (7): 1830–46. PMID 13672973.