Purification and characterisation of angiotensin I converting enzyme inhibitory peptides from lysozyme hydrolysates

Hen egg white lysozyme (HEWL) was hydrolysed with trypsin, papain and a combination of the two. The prepared hydrolysates exhibited ACE inhibitory activity. The hydrolysates were fractionated using ultrafiltration and reverse phase-high performance liquid chromatography (RP-HPLC). Three fractions, which showed the highest ACE inhibitory activities, were purified by RP-HPLC. They were the F(7) (from papain trypsin hydrolysate), F(8) (from papain hydrolysate) and F(3) (from trypsin hydrolysate) fractions. The IC(50) values were 0.03, 0.155 and 0.23 mg/ml for F(7), F(8) and F(3), respectively. The F(7) fraction was the most potent ACE inhibitor peptide, and was composed of 12 amino acids, Phe-Glu-Ser-Asn-Phe-Asn-Thr-Gln-Ala-Thr-Asn-Arg (MW: 1428.6 Da). Lineweaver-Burk plots suggest that the F(7) peptide acts as an uncompetitive inhibitor against ACE. The kinetic parameters (K(m), V(max), and K(i)) for the F(7) peptide were measured and compared to the control. (C) 2011 Elsevier Ltd. All rights reserved.