Biology:Formimidoyltetrahydrofolate cyclodeaminase

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formimidoyltetrahydrofolate cyclodeaminase
Identifiers
EC number4.3.1.4
CAS number9032-05-7
Databases
IntEnzIntEnz view
BRENDABRENDA entry
ExPASyNiceZyme view
KEGGKEGG entry
MetaCycmetabolic pathway
PRIAMprofile
PDB structuresRCSB PDB PDBe PDBsum
Gene OntologyAmiGO / QuickGO

In enzymology, a formimidoyltetrahydrofolate cyclodeaminase (EC 4.3.1.4) is an enzyme that catalyzes the chemical reaction

5-formimidoyltetrahydrofolate [math]\displaystyle{ \rightleftharpoons }[/math] 5,10-methenyltetrahydrofolate + NH3

Hence, this enzyme has one substrate, 5-formimidoyltetrahydrofolate, and two products, 5,10-methenyltetrahydrofolate and NH3.[1]

This enzyme belongs to the family of lyases, specifically ammonia lyases, which cleave carbon-nitrogen bonds. The systematic name of this enzyme class is 5-formimidoyltetrahydrofolate ammonia-lyase (cyclizing 5,10-methenyltetrahydrofolate-forming). Other names in common use include formiminotetrahydrofolate cyclodeaminase, and 5-formimidoyltetrahydrofolate ammonia-lyase (cyclizing). This enzyme participates in folate metabolism by catabolising histidine and adding to the C1-tetrahydrofolate pool.

In mammals, this enzyme can be found as part of a bifunctional enzyme in a single polypeptide with glutamate formimidoyltransferase (EC 2.1.2.5), the enzyme activity that catalyses the previous step in the histidine catabolic pathway.[2] This arrangement allows the 5-formimidoyltetrahydrofolate intermediate to move directly from one active site to another without being released into solution, in a process called substrate channeling.[3]

Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1O5H, 1TT9, and 2PFD.

References

  1. Rabinowitz JC; Pricer WE (1956). "Formiminotetrahydrofolic acid and methenyltetrahydrofolic acid as intermediates in the formation of N10-formyltetrahydrofolic acid". J. Am. Chem. Soc. 78 (21): 5702–5704. doi:10.1021/ja01602a073. 
  2. "The bifunctional enzyme formiminotransferase-cyclodeaminase is a tetramer of dimers". J. Biol. Chem. 255 (19): 9474–8. 10 October 1980. doi:10.1016/S0021-9258(19)70586-9. PMID 7410436. http://www.jbc.org/cgi/reprint/255/19/9474. 
  3. "The crystal structure of the formiminotransferase domain of formiminotransferase-cyclodeaminase: implications for substrate channeling in a bifunctional enzyme". Structure 8 (1): 35–46. 2000. doi:10.1016/S0969-2126(00)00078-2. PMID 10673422.