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

摘要

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 ultra-filtration 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_4, 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.