Identification and quantification of ACE-inhibiting peptides in enzymatic hydrolysates of plant proteins

Enzymatic hydrolysis of proteins from rice, soy, pea and wheat, with both chymotrypsin and thermolysin, resulted in hydrolysates, which are efficient inhibitors of the angiotensin-converting enzyme (ACE). IC₅₀ values of the hydrolysates were between 27 and 39mg/l, which is comparable to enzymatically hydrolysed whey protein. A significant increase of the ACE-inhibiting effect was observed following butanol extraction due to accumulation of hydrophobic peptides (IC₅₀ between 12 and 21mg/l). Based on the identification and quantification of individual tryptophan-, tyrosine- and phenylalanine-containing dipeptides, 50-80% of the total ACE-inhibiting potential of butanol extracts from plant protein hydrolysates could be explained. Compared to hydrolysates from whey protein, where the inhibitory effect can almost exclusively be attributed to Ile-Trp, the ACE inhibition by plant protein hydrolysates is caused by a variety of peptides, in particular tyrosine-containing peptides. Hydrolysates of plant proteins are promising ingredients for the development of functional foods.