Purification and characterization of angiotensin I-converting enzyme inhibitory peptides from enzymatic hydrolysate of hen egg white lysozyme

The aims of this study were to explore new functional bioactivity of hen egg white lysozyme (HEWL) protein hydrolysate and to identify potential angiotensin I-converting enzyme (ACE) inhibitory peptides from HEWL. The protein was hydrolyzed by gastrointestinal enzymes, including pepsin, a-chymotrypsin and trypsin, under simulated physiological conditions, and the hydrolysate exhibited potent ACE inhibitory activity with an IC50 value of 15.6 +/- 1.4 mu g/mL. Three novel ACE inhibitory peptides, specifically, Met-Lys-Arg, Arg-Gly-Tyr and Val-Ala-Trp with IC50 values of 25.7 +/- 0.2, 61.9 +/- 0.1 and 2.86 +/- 0.08 mu M, respectively, were isolated from the hydrolysate of HEWL in two stages of reverse-phase high-performance liquid chromatography (RP-HPLC), and their sequences were analyzed by UPLC-MS/MS. Kinetics studies suggested that the purified peptides were all competitive inhibitors; preincubation experiments implied that the peptide Arg-Gly-Tyr was a true substrate and that the other two peptides were true ACE inhibitors. These results indicate that HEWL may become an effective source of ACE inhibitory peptides. This study reveals the antihypertensive bioactivity of HEWL protein hydrolysate and provides further evidence that eggs are an excellent source of health-promoting food: (C) 2011 Elsevier Ltd. All rights reserved.