Characterization of Peptides and Proteins with Enzymes

Abstract

This chapter focuses on the characterization of peptides and proteins with enzymes. The chapter highlights that since the fundamental work of Fred Sanger on the structure of insulin, an increasing amount of research has been undertaken to determine the amino acid sequences in proteins and peptides. It is useful to degrade the proteins to be analyzed with proteolytic enzymes because the specificity of enzymes permits the isolation of uniform fragments. The “spectrum” of the peptides obtained in this way is sometimes characteristic of a certain protein. The action of peptidases on individual peptides allows some determination of amino acid sequences. This chapter discusses that during hydrolysis of proteins to peptides, the high specificity of tripsin permits the isolation of defined fragments. Trypsin splits peptide bonds wherever the basic amino acids, lysine and arginine, occur; thus the carboxyl group of these amino acids is liberated. In this way peptides with a basic amino acid at the carboxyl end are obtained. Only two exceptions are known: trypsin does not hydrolyze peptide bonds if the α-amino group of lysine or arginine is free; or lysine is followed by proline in the peptide chain.