Effect of lysine residues on the deamidation reaction of asparagine side chains

The effect of lysine residues on the deamidation reaction of the asparagine side chain has been studied on the peptide Ac-Cys-Lys-Asn-Gly-Gln-Thr-Asn-Cys-NH2 and on its lysine-acetylated derivative in a wide range of pH values. The a mino acid sequence of these peptides is similar to the local sequence flank ing the labile Asn-67 in RNAse A. The experimental data show that Lys influ ences both the deamidation rate and the relative yield of the two reaction products, i.e., the aspartic acid and beta-aspartic acid containing peptide . These effects are pH dependent and can be rationalized based on the mecha nism previously proposed for the deamidation reaction via succinimide deriv ative. (C) 2000 John Wiley & Sons, Inc.