Mass spectrometric characterization of peptides derived by peptic cleavage of bovine β-casein

This study investigated the digestion of the milk protein β-casein with pepsin under gastro-analogous conditions. Peptide sequences were identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with post-source decay as well as liquid chromatography–tandem mass spectrometry by means of database searching. The new software tool, Mascot Distiller, improved the identification rate remarkably. In the case of small peptides, such as di- and tri-peptides, which are promising candidates for intestinal absorption and possible biological effects, identification was possible only after spectrum simulation and manual matching. A list of 41 identified peptides having 2–36 amino acids is given, and unexpected cleavage sites for pepsin are reported. Sequence coverage was 75%.