Enzymatic approach to the synthesis of a lysine-containing sweet peptide, N-acetyl-L-phenylalanyl-L-lysine.

Abstract

A sweet tasting peptide containing the l-Iysine residue, yV-acetyl-l-phenylalanyl-l-lysine, was synthesized from /V-acetyl-l-phenylalanine ethyl ester (Ac-Phe-OEt) as donor and l-lysine esters as acceptor nucleophiles by an α-chymotrypsin catalyzed reaction. It was revealed by HPLC analysis that the reaction proceeded most satisfactorily at pH 9 within 3 min in a reaction system containing 100 mM Ac-Phe-OEt, equimolar esters of lysine and 10 μm of the enzyme, where the product yield based on the donor concentration was 53 % for ethyl, 67 % for w-butyl and 31 % for benzyl esters. The highest reaction yield (75 %) was attained by using a double molar excess of lysine /i-butyl ester. The present results suggest that α-chymotrypsin may become a useful tool for the synthesis of peptides containing basic amino acids.