Identification and Characterization of Gastrointestinal-Resistant Angiotensin-Converting Enzyme Inhibitory Peptides from Egg White Proteins.

Abstract

Egg proteins are recognized as excellent sources of bioactive peptides, such as angiotensin-converting enzyme inhibitory (ACEi) peptides. Oral administration of a thermolysin-digested egg white hydrolysate (T-EWH) caused a significant blood pressure reduction in spontaneously hypertensive rats; a further ACEi assay implied that its ACEi activity was enhanced after in vitro gastrointestinal (GI) digestion. These results indicated that T-EWH contained ACEi peptides resisting GI digestionand/or being further released during GI digestion. Therefore, the objective of this study was to identify these responsibleACEi peptides from T-EWH. The conventionally activity-guided fractionation was applied, coupled with a synchronized GI digestion throughout, during which both peptide yield and ACEi activity before and after the GI digestion were measured. Finally, six ACEi peptides (LAPYK, LKISQ, LKYAT, INKVVR, LFLIKH, and LGHWVY) with good GI resistance were identified with IC50 values <20 μM, especially LKYAT (0.09 μM). The structure-activity relationship of these peptides was discussed. The discovery ofGI-resistant ACEi peptides could further support the application of egg white proteins as functional food ingredients.