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Leukotriene-A4 hydrolase is an enzyme that catalyzes the reaction which converts Leukotriene A4 to Leukotriene B4. It is a bifunctional zinc enzyme (EC 3.3.2.6) with different amino acids attached to it to aid in the catalysis of the reaction. It also acts as an aminopeptidase. Leukotriene-A4 hydrolase is a cytosolic protein and is found in almost all mammalian cells, tissues and organelles that have been examined.
Function
This enzyme belongs to the family of hydrolases, specifically those acting on ether bonds (ether hydrolases). The systematic name of this enzyme class is (7E,9E,11Z,14Z)-(5S,6S)-5,6-epoxyicosa-7,9,11,14-tetraenoate hydrolase. Other names in common use include LTA4 hydrolase, LTA4H, and leukotriene A4 hydrolase. This enzyme participates in arachidonic acid metabolism.
Catalyzed reaction
The chemical reaction catalyzed by LTA4H.
Leukotriene A4 Hydrolase catalyzes the reaction which converts leukotriene A4 to leukotriene B4. The Leukotriene A4 structure contains an epoxide ring functional group, which are highly reactive due to its ring strain making them extremely electrophilic. This drives the reaction forward, favouring the products Leukotriene B4. Leukotriene A4 hydrolase adds a water molecule across the epoxide ring on Leukotriene A4. The addition of the water molecule opens the epoxide ring and causes the formation of the Hydroxy group at the carbon attached to the oxygen from the epoxide. The second carbon involved in the epoxide ring remains the same resulting in leukotriene B4. The water molecule attacking the double bond also forms into a hydroxy group after work-up. The product of the reaction is Leukotriene B4.
Structure
As of late 2007, 4 structures have been solved for this class of enzymes, with PDB accession codes 1GW6, 1H19, 1HS6, and 1SQM.
Evans JF, Dupuis P, Ford-Hutchinson AW (1985). "Purification and characterisation of leukotriene A4 hydrolase from rat neutrophils". Biochim. Biophys. Acta. 840 (1): 43–50. doi:10.1016/0304-4165(85)90160-6. PMID3995081.
Crystallographic structure of LTA4H (rainbow colored N-terminus = blue, C-terminus = red) complexed with the protease inhibitor bestatin (space-filling model, carbon = white, oxygen = red, nitrogen = blue) based on the PDB: 1HS6 structure.
