Biotransformation of enones with biocatalysts — two enone reductases from Astasia longa

The stereochemistry and mechanism in the reduction of the C–C double bond of carvone by the cultured cells of Astasia longa, a nonchlorophyllous cell line classified in Euglenales, was studied. The reduction of the C–C double bond of carvone with the cultured cells involved the anti-addition of hydrogen atom from the si face at the α-position and the re face at the β-position of carbonyl group. Two different enone reductases were isolated from the cultured cells of A. longa. Both reductases catalyzed stereospecifically the anti-addition of hydrogen atoms from the si face at C-1 and the re face at C-6. However, one of the reductases participated in a hydrogen transfer of the pro-4R hydrogen of NADH to C-6 position of carvone and the other used the pro-4S hydrogen of NADH.