Bifunctional zinc metalloenzyme that comprises both epoxide hydrolase (EH) and aminopeptidase activities. Acts as an epoxide hydrolase to catalyze the conversion of LTA4 to the pro-inflammatory mediator leukotriene B4 (LTB4). Has also aminopeptidase activity, with high affinity for N-terminal arginines of various synthetic tripeptides. In addition to its pro-inflammatory EH activity, may also counteract inflammation by its aminopeptidase activity, which inactivates by cleavage another neutrophil attractant, the tripeptide Pro-Gly-Pro (PGP), a bioactive fragment of collagen generated by the action of matrix metalloproteinase-9 (MMP9) and prolylendopeptidase (PREPL). Involved also in the biosynthesis of resolvin E1 and 18S-resolvin E1 from eicosapentaenoic acid, two lipid mediators that show potent anti-inflammatory and pro-resolving actions. H2O + leukotriene A4 = leukotriene B4 (5S,6S)-epoxy-(18R)-hydroxy-(7E,9E,11Z,14Z,16E)-eicosapentaenoate + H2O = resolvin E1 (5S,6S)-epoxy-(18S)-hydroxy-(7E,9E,11Z,14Z,16E)-eicosapentaenoate + H2O = 18S-resolvin E1 Release of the N-terminal residue from a tripeptide. Binds 1 zinc ion per subunit. Inhibited by bestatin. The epoxide hydrolase activity is restrained by suicide inactivation that involves binding of LTA4 to Tyr-379. 4-(4-benzylphenyl)thiazol-2-amine (ARM1) selectively inhibits the epoxide hydrolase activity. Lipid metabolism; leukotriene B4 biosynthesis. Monomer. Phosphorylation at Ser-416 inhibits leukotriene-A4 hydrolase activity. activity. Belongs to the peptidase M1 family.