Carboxypeptidase A-catalyzed dipeptide synthesis in organic media

The carboxypeptidase A-catalyzed syntheses of dipeptides from L-amino acids (Phe, Tyr, Trp, Leu and Ile) were studied in various water-miscible (acetone, acetonitrile, ethanol, methanol and 1,4-dioxane) organic solvents. The highest yield (43%) was achieved in acetonitrile with L-Phe as substrate, after a 24-h incubation. The optimal conditions of Phe-Phe synthesis in acetonitrile were determined. For maximal conversion 1.2 mM L-Phe, 1.4 mg ml-1 enzyme and about 10% water are needed in buffered aqueous acetonitrile (pH 5.5) at 30 degrees C.