LAUSR

Abstract The synthesis of chiral amines as important pharmaceutical and fine chemical building blocks can be carried out with amine transaminases. The reaction equilibrium is often unfavorable. There are several methods to shift the equilibrium by co-product removal. One strategy employs isopropylamine as co-substrate resulting in the co-product acetone which can easily be evaporated under reduced pressure. However, many amine transaminases do not accept isopropylamine without further protein engineering. A subtler and generally applicable method uses alanine as co-substrate. A lactate dehydrogenase and a glucose dehydrogenase are added to remove the co-product pyruvate. Drawbacks are high costs for enzyme production and the addition of high amounts of biomass to reaction mixtures. We overcame these drawbacks by co-expression of an amine transaminase with a lactate dehydrogenase and a glucose dehydrogenase in a recombinant Escherichia coli strain. We further demonstrated the applicability on preparative scale. We used the E. coli cell free extract in reactions with up to 74 g/L substrate load achieving yields of >95% in reaction volumes of 10 mL–200 mL.