Angiotensin-converting enzyme inhibitory effects of whey protein hydrolyzate prepared using Protamex

Enzymatic hydrolyzates from whey protein concentrate (WPC) were investigated for in vitro inhibition of angiotensin I-converting enzyme (ACE). Alcalase, Trypsin, Protamex, Neutrase, and Flavozyme were used to hydrolyze the WPC (WPH). When compared to WPC inhibitory efficiency ratio (IER, % inhibition/protein content) 79.25%/mg/ml, WPH samples made using Trypsin (IER 461.58%/mg/ml) and Protamex (IER 443.88%/mg/ml) showed higher ACE inhibitory effects. The ACE inhibitory effects of the WPHs made from Trypsin and Protamex were similar, but the effects by Protamex as the enzyme were still much lower than those by Trypsin. Therefore, the WPH prepared using Protamex was employed to conduct additional experiments with respect to commercial applications. The WPH made using Protamex had the highest ACE inhibitory effects at 5 h of hydrolysis time (55.50%), and recovery was 70.15%. Kinetic studies of the Protamex WPH showed mixed-type inhibition. Furthermore, ACE inhibitory peptides from this WPH were purified using RP-HPLC with a C-18 column. The purified ACE inhibitory peptides had an IER value of 6303.34%/mg/ml. The results of this study suggest that WPH made by Protamex may have potential alternative antihypertensive effects for cardiovascular disease.