Terminal Amino Acids in Peptides and Proteins

Abstract

Publisher Summary This chapter focuses on terminal amino acids in peptides and proteins. Adequate study of terminal amino acids might provide useful tools for characterizing some of the chemical differences underlying biological specificities. It would in general be especially desirable to have an added index of difference or similarity between protein molecules that could be used more precisely than amino acid composition. The ideal solution to this problem would involve removal of terminal amino acids from a peptide of any length, one at a time, without alteration of the remaining peptide. The terminal amino acid approach offers the promise of providing a chemical means of testing some of the hypotheses of peptide arrangement in proteins. The two features of protein structure that have been definitely established are the constituent amino acid residues and the recurrent peptide linkage. Proteolytic enzymes that split off terminal amino acids should be ideally adaptable for purposes of identification. The value of an individual method for the identification of a terminal amino acid depends upon the purpose to which it is to be put and the type of material to be studied. Most of the methods reviewed should be adequate for identifying dipeptides. In the establishment of amino acid sequence in the natural dipeptides anserine and carnosine and in the natural tripeptide glutathione the trinitrotoluene condensation proved of key value for all three peptides. The study of terminal amino acids alone, in protein, would appear to have a working basis in procedures already developed. To unravel the amino acid sequence of the peptides and the proteins, the terminal amino acid seems to be a logical point at which to begin.