A Novel Approach to Enzymatic Peptide Synthesis Using Highly Solubilizing Nα-Protecting Groups of Amino Acids

Abstract

A novel strategy in kinetically controlled enzymatic peptide synthesis is described. Various amino acid derivatives with charged, highly solubilizing Nα-protecting groups were prepared and used in synthesis reactions. These protecting groups strongly increase both solubility of the amino acid substrates in purely aqueous medium as well as, in the case of α-chymotrypsin-catalyzed reactions, enzyme activity. It is possible to operate at extremely high electrophile concentrations up to 1.5 mol/1 and with equimolar nucleophile concentrations. As a consequence of this solubilizing effect, very high yields up to 93% were obtained in the enzymatic synthesis of several model peptides with different proteases in purely aqueous medium. The use of an organic cosolvent is no longer necessary. In continuous α-chymotrypsin-catalyzed production of kyotorphin (Tyr-Arg), a space-time yield of up to 13.4 kg/(l•d) was achieved. Scalability of this strategy to a 72 mole (400 1) batch experiment has been demonstrated successf...