ACE inhibitory peptides and antioxidant peptides derived from in vitro digestion hydrolysate of hen egg white lysozyme

Lysozyme from hen egg white is a well-known antimicrobial protein with high ratio of hydrophobic and positively charged amino acid residues. In order to explore functional bioactivities of enzymatic hydrolysates of lysozyme, the protein was subjected to a simulated gastrointestinal digestion and the resulting hydrolysate (LPH2) showed a strong competitive angiotensin I-converting enzyme (ACE) inhibitory activity (IC50 = 12.6 μg/ml) and a remarkable antioxidant activity. The LPH2 was fractionated using a 3 kDa cut-off membrane and the obtained permeate LPH2–3 kDa was analysed by MALDI-TOF-TOF MS. Using this technology, 38 different peptides were identified and some of these peptides were well fit with structure requirements of ACE inhibitory peptides and/or antioxidant peptides. The findings from this study suggest that the protein containing high proportion of hydrophobic and positively charged residues have the potential to generate multifunctional peptides, and these peptides would be beneficial ingredient to be used in functional foods.