Converts hepoxilin A3 into trioxilin A3. Highly specific for the substrate, having only slight activity with other epoxides such as leukotriene A4 and styrene oxide . Hepoxilin A3 is an hydroxy-epoxide derivative of arachidonic acid that is formed via the 12-lipoxygenase pathway . It is probable that this enzyme plays a modulatory role in inflammation, vascular physiology, systemic glucose metabolism and neurological function . In vertebrates, five epoxide-hydrolase enzymes have been identified to date: EC 126.96.36.199 (leukotriene-A4 hydrolase), EC 188.8.131.52 (hepoxilin-epoxide hydrolase), EC 184.108.40.206 (microsomal epoxide hydrolase), EC 220.127.116.11 (soluble epoxide hydrolase) and EC 18.104.22.168 (cholesterol 5,6-oxide hydrolase) .