Production of chiral β-amino acids using ω-transaminase from Burkholderia graminis

• A (S)-enantioselective ω-transaminase from Burkholderia graminis C4D1M was biochemically characterized.
• The enzyme showed broad substrate specificity towards aromatic β-amino acids and it was utilized to kinetically resolve β-amino acids.
• Benzaldehyde was used as an amino acceptor for the first time to kinetically resolve optically pure aromatic β-amino acids.
• The enzyme was modelled and its active site was analyzed.

Optically pure β-amino acids are of high pharmacological significance since they are used as key ingredients in many physiologically active compounds. Despite a number of enzymatic routes to these compounds, an efficient synthesis of β-amino acids continues to pose a major challenge for researchers. ω-Transaminase has emerged as an important class of enzymes for generating amine compounds. However, only a few ω-transaminases have been reported so far which show activity towards aromatic β-amino acids. In this study, (S)-ω-transaminase from Burkholderia graminis C4D1M has been functionally characterized and used for the production of chiral aromatic β-amino acids via kinetic resolution. The enzyme showed a specific activity of 3.1 U/mg towards rac-β-phenylalanine at 37 °C. The Km and Kcat values of this enzyme towards rac-β-phenylalanine with pyruvate as the amino acceptor were 2.88 mM and 91.57 min−1 respectively. Using this enzyme, racemic β-amino acids were kinetically resolved to produce (R)-β-amino acids with an excellent enantiomeric excess (>99%) and ∼50% conversion. Additionally, kinetic resolution of aromatic β-amino acids was performed using benzaldehyde as a cheap amino acceptor.