Epoxide hydrolase that catalyzes the final step in the biosynthesis of the pro-inflammatory mediator leukotriene B4. Has also aminopeptidase activity (By similarity). H2O + leukotriene A4 = leukotriene B4 Binds 1 zinc ion per subunit. Inhibited by bestatin. Subject to suicide inhibition by leukotriene A4 (By similarity). Lipid metabolism; leukotriene B4 biosynthesis. Phosphorylation at Ser-416 inhibits enzymatic activity. Belongs to the peptidase M1 family.