Abstract: Cholecystokinin(CCK) is a polypeptide hormones with gastrointestinal, biliar and brain activities. Many methods were reported on the synthesis of the C-terminal octapeptide. Enzymatic techeiques possess numerous advantages over chemical techniques for the formation of the peptide bond. Here we reported an enzyme-catalyzed method to synthesize a cholecystokinin tetrapeptide(Phac-Met-Gly-Trp-Met-OEt) fragment. It was synthesized by coupling Phac-Met-OEt with Gly-OMe·HCl, Trp-OMe and Met-OEt successively, these three steps were catalyzed by α-chymotrpsin, papain and α-chymotrpsin respectively. The influence factors on the reaction including the choice of enzymes, solvents, acyl donor and buffer contents were also studied. All the reaction intermediates and products were confirmed to have the correct molecular mass by the results of FAB-MS.

Key words: CCK-8, Enzyme-catalyzed method, α-Chymotrpsin, Papain