STEREOSELECTIVITY OF CHEMICALLY-MODIFIED ALPHA-CHYMOTRYPSIN AND IMMOBILIZED LIPASES

The chemical modification of alpha-chymotrypsin by monomethoxypolyethylene glycol and the immobilization of lipases from Candida rugosa and C. antarctica on several supports changes the enantioselectivity of the enzymatic derivatives compared with the behaviour of the native enzymes. Hydrolysis and synthesis of esters have been used as reaction tests. This alteration could be related to the rigidification of the 'h' subsite of the enzyme by the effect of those processes. Technical variables such as time, temperature, stirring speed etc. do not alter the observed enantioselectivity. The presence or absence of water changes slightly the enantioselectivity in the synthesis of esters catalysed by immobilized lipases in dry isooctane.