Developed by Swedish biochemist, Pehr Edman, over half a century ago2, Edman degradation involves the cyclical degradation of peptides that follows three main steps. Firstly, a reagent called phenyl isothiocyanate (PITC) is coupled to the α-amino group of a peptide or protein. The amino-terminal amino acid is then cleaved through cyclization and the resultant product is stabilized in aqueous acid to a phenylthiohydantion (PTH) amino acid. This process is repeated until the length of the amino acid has been degraded. The identity of each PTH-amino acid is determined using chromatographic or electrophoretic techniques, thereby enabling almost entire peptide sequences to be calculated.
While Edman degradation is not as popular as mass spectrometry-based sequencing methods, it can be useful in characterizing the N-terminus of a protein. Moreover, the method has since been miniaturized and coupled with gas-phase sequencers, expanding its power of application3.
However, Edman degradation still has some limitations. A common limitation of Edman degradation is that it is suited to sequencing short peptides (<30 to 50 residues) due to high error propensity. It is also low throughput (e.g., around 40 minutes per amino acid), and unable to sequence N-terminally inaccessible peptides (e.g., acetylated)2. This is why to capture the full sequence of a protein quickly, researchers often turn to mass spectrometry means.