chapter  7
Chemical Methods of Amino Acid Sequence Analysis from Carboxy Terminal End
ByM. Rangarajan
Pages 10

The amino acid derivative could be identified by hydrolyzing it to the parent amino acid with acid or alkali. In contrast to N-terminal group determination and sequential analysis of proteins and peptides from the N-terminal end, only a few chemical methods are available for the determination of C-terminal groups and sequential degradation of proteins and peptides from the C terminus. The most commonly used procedure for the determination of protein and peptide sequences from the C-terminal end is the use of exopeptidases, namely, carboxy-peptidases. The peptidyl thiohydantoin was selectively cleaved with ace-tohydroxamic acid, and the C-terminal amino acid was determined by difference amino acid analysis of the peptide before and after the degradation cycle. Side-chain carboxyl groups of aspartic and glutamic acids were also rearranged in the process to the corresponding amines. The sequence of four residues from the C-terminal end of a 22-residue protein fragment was determined.