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 F3 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 μM exhibited the highest ACE inhibitory activity. Kinetic studies revealed that the F3 peptide acts as a non-competitive inhibitor against ACE. The interaction between the F3 peptide and ACE was further scrutinized by fluorescence spectroscopy and molecular modeling techniques. The binding of the F3 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-Ι to the strong vasoconstrictor angiotensin-ΙΙ. Inhibition of ACE by decreasing the concentration of angiotensin ΙΙ 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.

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