Catalyses the hydrolysis of?trans-substituted epoxides, such as?trans-stilbene oxide, as well as various aliphatic epoxides derived from fatty-acid metabolism [7]. It is involved in the metabolism of arachidonic epoxides (epoxyeicosatrienoic acids; EETs) and linoleic acid epoxides. The EETs, which are endogenous chemical mediators, act at the vascular, renal and cardiac levels to regulate blood pressure [4,5]. The enzyme from mammals is a bifunctional enzyme: the C-terminal domain exhibits epoxide-hydrolase activity and the N-terminal domain has the activity of EC?3.1.3.76, lipid-phosphate phosphatase [1,2]. Like EC?3.3.2.9, microsomal epoxide hydrolase, it is probable that the reaction involves the formation of an hydroxyalkyl¡ªenzyme intermediate [4,6]. The enzyme can also use leukotriene A4, the substrate of EC?3.3.2.6, leukotriene-A4?hydrolase, but it forms 5,6-dihydroxy-7,9,11,14-eicosatetraenoic acid rather than leukotriene B4?as the product [9,10]. In vertebrates, five epoxide-hydrolase enzymes have been identified to date: EC?3.3.2.6?(leukotriene-A4?hydrolase), EC?3.3.2.7?(hepoxilin-epoxide hydrolase), EC?3.3.2.9?(microsomal epoxide hydrolase), EC?3.3.2.10?(soluble epoxide hydrolase) and EC?3.3.2.11?(cholesterol 5,6-oxide hydrolase) [7].
