Peptidome Analysis of Human Milk β-Casein in vitro Neonatal Digestive Model by Matrix-assisted Laser Desorption/Ionization-Time-of-Flight Tandem Mass Spectrometry

Human milk β-casein was digested in vitro by simulated neonatal digestive model to explore the peptidome of human β-casein digested in neonate by matrix-assisted laser desorption/ionization-time-of-flight tandem mass spectrometry (MALDI-TOF/TOF). The accelerating voltage was 20 kV. The laser wavelength was 337 nm and the frequency was 200 Hz. Ion extraction delay was 330 ns. Final mass spectra were produced by averaging 2000 laser shots taken at five different positions within each spot. The peptides scanning range is from m/z 500 to m/z 5000. A total of 26 peptides were identified in the molecular weight range of 1000–4000 Da, and no bioactive peptides were found. Instead, we found nine bioactive peptide precursors which include four ACE (Angiotensin converting enzyme) inhibitory peptide precursors, two CPP (Caseinophosphopeptide) precursors, two antioxidant peptide precursor and one immune active peptide precursor. Most of the bioactive peptide precursors might be further digested into biologically active peptides by proteases according to the present cleavage sites.

Graphical abstractThe peptidome of human βcasein in vitro neonatal digestive model was analyzed by MALDI-TOF/TOF. A total of 26 peptides and nine bioactive peptide precursors including four ACE inhibitory, two CPP, two antioxidant and one immune active precursors were identified. According to the protease enzymatic cleavage sites, the peptide precursors can be converted to the active peptides.Figure optionsDownload full-size imageDownload as PowerPoint slide