Angiotensin I converting enzyme-inhibiting peptides purified from elastase-degraded elastin prepared from pig aorta

Background: Many peptides are produced from food proteins during the manufacturing of various functional foods; unexpected and valuable physiological activities are frequently identified in such released peptides. Elastin, which normally exists as an insoluble elastic fiber, is being used as a new health food material in accordance with the progress in solubilization techniques for elastin. Objective: To evaluate the usefulness of elastin as a material for functional foods, we prepared highly pure, water-soluble elastin from pig aorta and evaluated its angiotensin-converting enzyme (ACE)-inhibitory activity. Method: Pure, water-soluble elastin was prepared from pig aorta using a hydrolyzing method employing a hot alkali reagent. Efficient enzymatic degradation of the elastin was achieved by using elastase that is specific for elastin. The ACE-inhibitory activities of elastin and of peptides obtained via enzymatic degradation were investigated. Three novel ACE-inhibiting peptides were purified from the degradation, and we investigated their ACE-inhibitory activities. Results: Highly pure, water-soluble elastin was prepared from pig aorta; this elastin preparation showed weak inhibitory activity (8.4% inhibition) against ACE. Surprisingly, 6-fold greater enzyme-inhibitory activity was observed for elastin peptides obtained from elastase-mediated degradation of the soluble elastin (48.0% inhibition). Among the enzymatically degraded elastin peptides, three were purified and their primary structures were newly characterized as Val-Tyr-Pro-Gly, Val-Gly-Val-Ala-Pro-Gly, and Gly-Tyr-Pro-Ile. All three peptides showed apparent ACE-inhibitory activity, and Val-Tyr-Pro-Gly exhibited the highest inhibitory capacity among them (60.6% inhibition). Conclusion: These results suggest that water-soluble elastin may serve as a functional food to exert a blood pressure-lowering effect in the body.