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Keywords:

  • chiral amines;
  • enantioselectivity;
  • enzyme catalysis;
  • transaminases

Abstract

Seven (R)-selective amine transaminases (R-ATAs) recently discovered by an in silico-based approach in sequence databases were produced recombinantly in Escherichia coli and subjected to partial purification by ammonium sulfate precipitation. A range of additives and various buffers were investigated to identify best conditions to ensure good storage stability and stable activity during biocatalysis. All enzymes show pH optima between pH 7.5–9. These R-ATAs were then applied in the asymmetric synthesis of twelve aliphatic, aromatic and arylaliphatic (R)-amines starting from the corresponding prochiral ketones using a lactate dehydrogenase/glucose dehydrogenase system to shift the equilibrium. For all ketones, at least one enzyme was found that allows complete conversion to the corresponding chiral amine having excellent optical purities >99% ee. Variations in substrate profiles are also discussed based on the phylogenetic relationships between the seven R-ATAs. Thus, we have identified a versatile toolbox of (R)-amine transaminases showing remarkable properties for application in biocatalysis.