Enzymatic peptide synthesis in frozen aqueous systems: Use of N-alpha-unprotected unusual acyl donors

alpha-Chymotrypsin (EC 3.4.21.1) was used for catalyzing the reaction of various N alpha-unprotected non-coded phenylalanine ester derivatives with H-Leu-NH2 and H-Arg-NH2 in frozen aqueous solution at -15 degrees C. Compared with reactions at room temperature, a significant yield increasing effect could be established. The kinetic parameters of ester hydrolysis show that most of the unusual acyl donors (compared with the coded phenylalanine methyl ester) are well accepted substrates for alpha-chymotrypsin.