Effect of organic cosolvent on kinetic resolution of tert-leucine by penicillin G acylase from Kluyvera citrophila.

Penicillin G acylase (PGA) from Kluyvera citrophila immobilized on Amberzyml was used for enantioselective hydrolysis of N-phenylacetylated-DL-tert-leucine (N-Phac-DL-Tle) to produce L-tert-leucine (L-Tle). The effects of various organic cosolvents on hydrolysis of N-Phac-DL-Tle have been investigated in aqueous-cosolvent medium. It was founded that the rate of PGA-catalyzed reaction was significantly affected by the presence of 2% (v/v) organic cosolvent concentration. The initial rate fell with increasing logP of the cosolvent, but for logP values less than -0.24 the rate was faster than in purely aqueous medium. Additionally, the relative rate increases with the increase of dielectric constant (epsilon) of organic cosolvents. The yields of L-Tle in all aqueous-cosolvent systems were above 95% with the enantiomeric excess (ee) of >99%.