Characterization of inhibition and stability of soy-protein-derived angiotensin I-converting enzyme inhibitory peptides

Angiotensin I-converting enzyme (ACE) inhibitory peptides were prepared from soy protein alkaline hydrolysate after ultrafiltration and cation exchange resin fractionation. The final yield was 14.42% (protein basis) and IC50 value was 0.065 mg of protein/ml. Soy-protein-derived ACE inhibitory peptides retained activity under various temperature and pH treatments. and showed resistance to in vitro digestion by gastrointestinal proteases. These peptides are competitive inhibitors as determined by the newly developed high-performance liquid chromatography (HPLC) continuous direct injection method. The two most potent peptides were sequenced after successive chromatographic isolation. They were Asp-Leu-Pro and Asp-Gly, with IC50 values of 4.8 and 12.3 mum, respectively. (C) 2002 Elsevier Science Ltd. All rights reserved.