PROBING THE SUBSTRATE-SPECIFICITY FOR LIPASES .2. KINETIC AND MODELING STUDIES ON THE MOLECULAR RECOGNITION OF 2-ARYLPROPIONIC ESTERS BY CANDIDA-RUGOSA AND RHIZOMUCOR-MIEHEI LIPASES

Racemic arylpropionic esters 1-3, precursors of therapeutically import ant non-steroidal antiinflammatory drugs, were subjected to hydrolyses in the presence of either Candida rugosa or Rhizomucor miehei crude l ipases. The hydrolyses of 1 and 2 proved to be highly enantioselective , whereas 3 was not transformed at all. Both the substrate specificity and the enantioselectivity of these lipases were explained through a molecular modeling study involving docking experiments between 1-3 and the amino acids forming the enzymes active-sites, whose three-dimensi onal structures were obtained from X-ray crystallographic data, follow ed by extensive conformational analysis on their computer-generated co mplexes. The results of this study also account for the high enantiose lective and good yielding hydrolysis of 3 (as the corresponding 2-chlo roethyl ester) catalyzed by CRL pretreated with 2-propanol, recently r eported in the literature, and lead to admit that such a treatment may operate very deep conformational changes on the amino acids of the en zyme active-site.