Identifying the Carboxy Terminal Amino Acid of a Protein

Abstract

Matsuo (2) proposed a chemical method for tritium labeling of C-terminal amino acid. The method involves the activation of the α-carboxyl group at the C-terminus by the formation of a mixed anhydride. This intramolecular anhydride gives oxazolone whose ring is easily opened by base-catalyzed hydrolysis. The C-terminal amino acid is then racemized and the a hydrogen of the C-terminal amino acid residue is tritiated. The resulting tritium labeled amino acid is separated by either paper chromatography or gas chromatography after hydrolysis, then subjected to subsequent analysis by a scintillation counter. A problem in this approach is the use of radioisotopes.