Separation, Purification, and Identification of Angiotensin I-Converting Enzyme Inhibitory Peptides from Walnut (Juglans regia L.) Hydrolyzate

Walnut proteins were hydrolyzed with pepsin, alcalase, and papain. A peptide that strongly inhibits angiotensin I-converting enzyme was isolated and purified from walnut protein hydrolyzates via ultrafiltration, Sephadex G-25, Superdex (TM) Peptide 10/300 GL, and reversed phase high-performance liquid chromatography. The in vitro inhibition of angiotensin I-converting enzyme was used as an indicator. The molecular structure and sequences of the angiotensin I-converting enzyme inhibitory peptides were identified through mass spectrometry and amino acid sequencing. The angiotensin I-converting enzyme inhibitory peptide from the walnut hydrolyzate was identified as Tyr-Glu-Pro (YEP) and its median inhibitory concentration was 0.29 mu mol/L.