Biphasic Reaction System Allows for Conversion of Hydrophobic Substrates by Amine Dehydrogenases

A novel amine dehydrogenase, “F-AmDH”, catalyzes the reversible reduction of prochiral ketones to chiral amines. However, many targeted hydrophobic substrates of F-AmDH show little to no solubility in an aqueous medium. The introduction of water-miscible organic solvents was unsuccessful because of AmDH deactivation. In a biphasic aqueous–organic system, F-AmDH, coupled with formate dehydrogenase (FDH), and hydrophilic co-factors are envisioned to remain in the aqueous phase while the hydrophobic substrate partitions between the phases. The advantages include a larger amount of total substrate present in the system, straightforward product removal, and reduced or negligible substrate and product inhibition. We succeeded in generating chiral amines from hydrophobic substrates that were previously unattainable because of the low solubility of the ketone substrate in aqueous medium. The partition coefficient played an important role in establishing optimal reaction conditions. Specific activity was found to ...