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

► Lysozyme was purified from egg white by superparamagnetic nanoparticles. ► In vitro digest of lysozyme exhibited ACE inhibitory and antioxidative potencies. ► Ultrafiltration improved the antioxidative activity of the final hydrolysate LPH2. ► Thirty-eight peptides in the LPH2–3kDa were identified by UPLC-MALDI-TOF-TOF MS. ► The identified peptides RGY, WIR and VAW were found to be dual-functional activities. 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=12.6μg/ml) and a remarkable antioxidant activity. The LPH2 was fractionated using a 3kDa cut-off membrane and the obtained permeate LPH2–3kDa 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.