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.