The present invention relates to proteins having an enzymatic activity of reducing substituted alkanones such as 3-methylamino-1-(2-thienyl)-propan-1-one. The invention furthermore relates to nucleic acids coding for said proteins, nucleic acid constructs, vectors, genetically modified microorganisms and to methods for preparing substituted (S)-alkanols, such as, for example, (S)-3-methylamino-1-(2-thienyl)-(S)-propanol.