(Cholesterol epoxide hydrolase or ChEH), is located in the endoplasmic reticulum and to a lesser extent plasma membrane of various cell types but most highly express in liver. The enzyme catalyzes the conversion of certain 3-hydroxyl-5,6-epoxides of cholesterol to their 3,5,6-trihydroxy products (see Cholesterol-5,6-oxide hydrolase). The function of ChEH is unknown.