IUBMB Enzyme Nomenclature


Accepted name: cholesterol-5,6-oxide hydrolase

Reaction: (1) 5,6α-epoxy-5α-cholestan-3β-ol + H2O = 5α-cholestane-3β,5α,6β-triol
(2) 5,6β-epoxy-5β-cholestan-3β-ol + H2O = 5α-cholestane-3β,5α,6β-triol

For diagram click here.

Glossary: cholesterol = cholest-5-en-3β-ol

Other name(s): cholesterol-epoxide hydrolase; ChEH

Systematic name: 5,6α-epoxy-5α-cholestan-3β-ol hydrolase

Comments: The enzyme appears to work equally well with either epoxide as substrate [3]. The product is a competitive inhibitor of the reaction. In vertebrates, five epoxide-hydrolase enzymes have been identified to date: EC (leukotriene-A4 hydrolase), EC (hepoxilin-epoxide hydrolase), EC (microsomal epoxide hydrolase), EC (soluble epoxide hydrolase) and EC (cholesterol 5,6-oxide hydrolase) [3].

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Levin, W., Michaud, D.P., Thomas, P.E. and Jerina, D.M. Distinct rat hepatic microsomal epoxide hydrolases catalyze the hydration of cholesterol 5,6 α-oxide and certain xenobiotic alkene and arene oxides. Arch. Biochem. Biophys. 220 (1983) 485-494. [PMID: 6401984]

2. Oesch, F., Timms, C.W., Walker, C.H., Guenthner, T.M., Sparrow, A., Watabe, T. and Wolf, C.R. Existence of multiple forms of microsomal epoxide hydrolases with radically different substrate specificities. Carcinogenesis 5 (1984) 7-9. [PMID: 6690087]

3. Sevanian, A. and McLeod, L.L. Catalytic properties and inhibition of hepatic cholesterol-epoxide hydrolase. J. Biol. Chem. 261 (1986) 54-59. [PMID: 3941086]

4. Fretland, A.J. and Omiecinski, C.J. Epoxide hydrolases: biochemistry and molecular biology. Chem. Biol. Interact. 129 (2000) 41-59. [PMID: 11154734]

5. Newman, J.W., Morisseau, C. and Hammock, B.D. Epoxide hydrolases: their roles and interactions with lipid metabolism. Prog. Lipid Res. 44 (2005) 1-51. [PMID: 15748653]

[EC created 2006]

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