Accepted name: formimidoyltetrahydrofolate cyclodeaminase
Reaction: 5-formimidoyltetrahydrofolate = 5,10-methenyltetrahydrofolate + NH3
Other name(s): formiminotetrahydrofolate cyclodeaminase; 5-formimidoyltetrahydrofolate ammonia-lyase (cyclizing)
Systematic name: 5-formimidoyltetrahydrofolate ammonia-lyase (cyclizing; 5,10-methenyltetrahydrofolate-forming)
Comments: In eukaroytes, occurs as a bifunctional enzyme that also has glutamate formimidoyltransferase (EC activity.
1.  Rabinowitz, J.C. and Pricer, W.E. Formiminotetrahydrofolic acid and methenyltetrahydrofolic acid as intermediates in the formation of N10-formyltetrahydrofolic acid. J. Am. Chem. Soc. 78 (1956) 5702–5704.
[EC created 1961, modified 2000]