INVERSION OF ENANTIOSELECTIVITY OF SERINE PROTEASES

The enantioselectivity of serine proteases in the transesterification of N-acetyl-(D,L)-phenylalanine esters with propan-1-ol in cyclohexane is strongly influenced by the leaving ability of the alcoholate group . Moreover the enantioselectivity is greatly influenced by the additio n of small amounts (0.33 M) of organic additives. Addenda with a small molecular volume like e.g. ethanol and acetonitrile increase the rate for the L-enantiomer whereas alcohols with bulky alkyl groups like e. g. tert-butanol and 2-methylbutan-2-ol enhance the activity of the enz yme towards the D-enantiomer. This enables a rational tuning of the en antioselectivity as was demonstrated for four different proteases (alp ha-chymotrypsin, subtilisin Carlsberg, Aspergillus oryzae protease, an d elastase).