Enzymatic Synthesis of Aliphatic Acyloins Catalyzed by Thermostable Transketolase

The thermostable transketolase from Geobacillus stearothermophilus (TKgst) was successfully engineered for the synthesis of aliphatic acyloins with varying carbon backbone lengths (C5−C10) based on protein structure‐guided studies. Efficient TKgst variants were identified with enhanced activities for substrate combinations of aliphatic aldehydes as acceptors together with aliphatic pyruvate homologues as donors. The TKgst single variant L382F was able to catalyze efficiently the transfer of the ketol group from hydroxypyruvate on all targeted aliphatic aldehydes (C3−C8) to give the corresponding 1,3‐dihydroxy ketones with good yields and excellent enantioselectivity. The combination of the H102L/H474S mutation previously designed for the improved utilization of aliphatic pyruvate homologues together with a F435I exchange gave the new variant H102L/H474S/F435I, which is able to transfer the acyl goup of 2‐oxobutyrate and 2‐oxovalerate to aliphatic aldehydes, giving mono hydroxylated ketones.