Characterization of enzymes specifically producing chiral flavor compounds (R)- and (S)-1-phenylethanol from tea (Camellia sinensis) flowers

1-Phenylethanol is a chiral flavor compound that has enantiomers, ( R )- and ( S )-1-phenylethanol, with different flavor properties. Given that isolating these enantiomers from plants is low yielding and costly, enzymatic synthesis presents an alternative approach. However, the genes/enzymes that specifically produce ( R )- and ( S )-1-phenylethanol in plants are unknown. To identify these enzymes in tea ( Camellia sinensis ) flowers, 21 short chain dehydrogenase (SDR) genes were isolated from tea flowers, cloned, and functionally characterized. Several recombinant SDRs in Escherichia coli exhibited activity for converting acetophenone to ( S )-1-phenylethanol (CsSPESs, >99.0%), while only one SDR produced ( R )-1-phenylethanol (CsRPES, 98.6%). A pair of homologue enzymes (CsSPES and CsRPES) showed a strong preference for NADPH cofactor, with optimal enzymatic reaction conditions of 45–55 °C and pH 8.0. Identification of the tea flower-derived gene responsible for specific synthesis of ( R )- and ( S )-1-phenylethanolsuggests enzymatic synthesis of enantiopure 1-phenylethanol is possible using a plant-derived gene.