Amination of ketones by employing two new (S)-Selective ω-transaminases and the His-tagged ω-TA from Vibrio fluvialis
Two recently identified (S)-selective ω-transaminases (ω-TAs) that originate from Paracoccus denitrificans (Strep-PD-ωTA, cloned with an N-terminal Strep-tag II) and Pseudomonas fluorescens (PF-ωTA) were employed for the asymmetric amination of selected prochiral ketones. The substrates tested were transformed into optically pure amines (>99% ee) with high conversion (up to >99%). The ω-TAs led to higher conversion in the absence of dimethyl sulfoxide as a cosolvent than in its presence (15%, v/v). Additionally, it was shown that a His-tagged recombinant transaminase from Vibrio fluvialis (His-VF-ωTA, cloned with an N-terminal His6-tag) showed for a single substrate, ethyl acetoacetate, significantly higher stereoselectivity for the amination compared to the corresponding commercial enzyme preparation (>99 vs. 50%).