The C-Terminal Determination of Polypeptide by the Selective Tritium-labeling. V. C-Terminal Cleavage of Peptide by the Action of Acetic Anhydride

Abstract

During the course of further investigation of Method B, which was previously proposed for the tritiation of C-terminal proline in the peptide chain, it was revealed that the C-terminal amino acid was cleaved to some extent under the heat-treatment of peptide in AcOH-Ac₂O solution. This type of C-terminal cleavage was confirmed gas- and paper-chromatographically and further evidences were also obtained by the C-terminal assay of the reaction products. In the present study, it was also revealed that non-C-terminal histidine residue in peptide chain underwent the hydrogen-tritium exchange reaction in its imidazole ring, when the peptide containing histidine residue was heated in a mixture of acetic anhydridetritiated water or acetic anhydride-[carboxy-³H] acetic acid in the absence of pyridine.