Purification and characterization of a novel angiotensin-I converting enzyme (ACE) inhibitory peptide derived from enzymatic hydrolysate of grass carp protein

Peptides inhibiting angiotensin-I converting enzyme (ACE, EC. 3.4.15.1) are possible cures of hypertension. Food-derived ACE-inhibitory peptides are particularly attractive because of reduced side effects. Previously, we reported ACE-inhibitory activity of grass carp protein hydrolysates. In this work, we report steps for purifying the ACE-inhibitory peptide from the hydrolysate and its biochemical properties. Following steps of ultrafiltration, macroporous adsorption resin, and two steps of reversed phase high performance liquid chromatography (RE-HPLC), a single Val-Ala-Pro (VAP) tripeptide was identified. The tripeptide with excellent ACE-inhibitory activity (IC(50) value of 0.00534 mg/mL) was a competitive ACE inhibitor and stable against both ACE and gastrointestinal enzymes of pepsin and chymotrypsin. This is the first report of food-derived VAP. The identified unique biochemical properties of VAP may enable the application of grass carp protein hydrolysates as a functional food for treatments of hypertension. The developed purification conditions also allow the production of VAP for pharmaceutical applications.