Identification of a novel angiotensin-I converting enzyme inhibitory peptide from ostrich egg white and studying its interactions with the enzyme

Ostrich egg white (OEW) proteins were hydrolyzed by trypsin to identify inhibitory peptides of angiotensin I-converting enzyme (ACE). The most active hydrolysate was obtained after 4 h of hydrolysis. It was further consecutively fractionized by ultrafiltration membrane and then was separated into nine fractions by reversed-phase high performance liquid chromatography (RP-HPLC). Among the fractions, the F-3 fraction with amino acid sequence of Ala-Phe-Lys-Asp-Glu-Asp-Thr-Glu-Glu-Val-Pro-Phe-Arg (MW: 1582.74 Da) and IC50: 80.2 mu M exhibited the highest ACE inhibitory activity. Kinetic studies revealed that the F-3 peptide acts as a non-competitive inhibitor against ACE. The interaction between the F-3 peptide and ACE was further scrutinized by fluorescence spectroscopy and molecular modeling techniques. The binding of the F-3 peptide to ACE was observed to occur via two classes of binding sites and F3 had more affinity to N-domain than C-domain. Industrial relevance: Angiotensin converting enzyme (ACE) can increase blood pressure by catalyzing the conversion of the inactive angiotensin-I to the strong vasoconstrictor angiotensin-II. Inhibition of ACE by decreasing the concentration of angiotensin II is of great importance. In this study, a thirteen-amino acid peptide was identified from Ostrich egg white (OEW) hydrolysates which can potently inhibit ACE. Thus, the identified peptide could be considered as a worthwhile peptide to control hypertension via using as a supplement for special food products. Furthermore, the results can be used as a model for studying the interaction of inhibitory peptides with ACE. (c) 2013 Elsevier Ltd. All rights reserved.