Bioamination of prochiral ketones using omega-transaminases

Omega-transaminases are pyridoxal-5-phosphate (PLP)-dependent enzymes that catalyze the transfer of an amino group from an amino donor to an aldehyde and/or ketone. In the present work, it was studied the asymmetric synthesis of primary amines from prochiral ketones. Four different substrates, containing heterocycles rings and planar structures, were evaluated towards two commercial enzymes and five omega-transaminases expressed heterologously in E. coli. Commercial enzymes were employed in the optimization of the reaction conditions and evaluation of the substrate scope, with conversions and ee higher than 99%. Regarding the five omega-transaminases expressed heterologously in E. coli, these enzymes were able to convert substrates into the desired products at a rate of 1.3 to 4.8%. Although the observed conversion values are still not satisfactory, the enantiomeric excesses obtained when using these enzymes were great to excellent (84 to > 99%), being a good starting point for further reaction and/or biocatalyst engineering.