ORGANIC-REACTIONS CATALYZED BY INSOLUBILIZED ENZYMES .2. INFLUENCE OF STRUCTURE OF THE ACYL DONOR IN SELECTIVITY OF ALPHA-CHYMOTRYPSIN

The enzymatic activity of a new insolubilized α-chymotrypsin (α-CT) on agarose is analyzed. The esterase activity was tested versus several synthetic isosteres of L-phenylalanine methyl ester. The insolubilized derivative hydrolyzes, with similar initial rates, m-Cl, o-Cl and p-Cl and phenylalanine esters in several organic-aqueous media. 1,4-Dioxane, DMF and THF were used as organic water-miscible solvents at 50-70%. Acetonitrile poisons the enzyme in hydrolytic conditions, which could be related to the acidic character of this solvent. In kinetically controlled peptide synthesis, the enzyme can act only with L-Phe and m-Cl esters, using several amino acids as nucleophiles. These differences in enzymatic activity are analyzed and explained according to alterations in the active site of the enzyme. DOR experiments showed that the insolubilized α-CT used in this work was not stereoselective versus the D or L form of amino acid in the hydrolysis of esters at pH 6 and in the kinetically controlled peptide synthesis. © 1990.