The reaction occurs in the opposite direction to that shown above. The enzyme participates in the menthol-biosynthesis pathway of Mentha plants. (+)-Pulegone, (+)-cis-isopulegone and (-)-menthone are not substrates. The enzyme has a preference for NADPH as the reductant, with NADH being a poor substitute . The enzyme is highly regioselective for the reduction of the endocyclic 1,2-double bond, and is stereoselective, producing only the 1R-configured product. It is a member of the short-chain dehydrogenase/reductase superfamily.
Croteau, R. and Venkatachalam, K.V. Metabolism of monoterpenes: demonstration that (+)-cis-isopulegone, not piperitenone, is the key intermediate in the conversion of (-)-isopiperitenone to (+)-pulegone in peppermint (Mentha piperita). Arch. Biochem. Biophys.249 (1986) 306–315. [DOI] [PMID: 3755881]
Ringer, K.L., McConkey, M.E., Davis, E.M., Rushing, G.W. and Croteau, R. Monoterpene double-bond reductases of the (-)-menthol biosynthetic pathway: isolation and characterization of cDNAs encoding (-)-isopiperitenone reductase and (+)-pulegone reductase of peppermint. Arch. Biochem. Biophys.418 (2003) 80–92. [DOI] [PMID: 13679086]