Multistep enzyme catalysed deracemisation of 2-naphthyl alanine

Kinetic parameters of D-amino acid oxidase from R. gracilis (DAAO) towards D-2-naphthyl alanine (D-2-NAla) and of L-aspartate amino transferase (L-AAT) from Escherichia coli towards 2-naphthyl pyruvate (2-NPA) were measured. The two enzymes were then combined in a one-pot reaction in which DAAO was used to generate 2-NPA which was the substrate of L-AAT in the presence of cysteine sulphinic acid (CSA) as an amino donor. The combined reactions afforded enantiomerically pure L-2-NAla in almost quantitative yield. The extremely low water solubility of 2-NAla can be partially overcome by running the biotransformation in suspension with higher formal concentration. In these conditions multiple enzyme additions are required.