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Formimidoyltetrahydrofolate cyclodeaminase

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EC number
  
4.3.1.4

IntEnz
  
IntEnz view

ExPASy
  
NiceZyme view

CAS number
  
9032-05-7

BRENDA
  
BRENDA entry

KEGG
  
KEGG entry

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

5-formimidoyltetrahydrofolate 5,10-methenyltetrahydrofolate + NH3

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

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. 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.

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

Formimidoyltetrahydrofolate cyclodeaminase Wikipedia