Methenyltetrahydrofolate cyclohydrolase

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


 * 5,10-methenyltetrahydrofolate + H2O $$\rightleftharpoons$$ 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. The systematic name of this enzyme class is 5,10-methenyltetrahydrofolate 5-hydrolase (decyclizing). Other names in common use include Citrovorum factor cyclodehydrase, cyclohydrolase, and formyl-methenyl-methylenetetrahydrofolate synthetase (combined). This enzyme participates in glyoxylate and dicarboxylate metabolism and one carbon pool by folate.

Structural studies
As of late 2007, 6 structures have been solved for this class of enzymes, with PDB accession codes, , , , , and.