Kazuhiro Ohki

Hydrolytic removal of acetyl-amino acid from acetyl- peptide in methanesulfonic acid

Acylation of the N-terminus of a protein with an acetyl (Ac) group is a common modification. Proteins and peptides with such blocking groups cannot be sequenced by Edman degradation. In the present study, we investigated the stability and susceptibility of the peptide bonds of Ac-X-Ala-Phe-OH (X = Gly, Ala, Pro, Tyr) towards aqueous methanesulfonic acid (MSA). This paper describes selective hydrolytic removal of Ac-amino acid from Ac-peptide in 70% MSA.

Selective removal of pyroglutamic acid residue from biologically active pyroglutamyl-peptides by aqueous methanesulfonic acid

A number of native proteins and peptides have been shown to possess a pGlu residue at the N-terminal, which is thought to afford protection against aminopeptidase digestion. Our recent studies [1–4] indicated that pGlu-peptide is highly sensitive to acid under mild conditions, generating not only the ringopened product of the pyrrolidone moiety of the pGlu residue, but also the cleavage product of the pGlu-peptide linkage, and pGlu-OH is selectively cleaved from pGlu-peptide in aqueous methanesulfonic acid (MSA). In this study, the selective removal of pGlu residue was examined from biologically active pGlu-peptides by aqueous MSA at 25°C.