Identification of novel angiotensin I-converting enzyme (ACE) inhibitory peptides from wheat gluten hydrolysate by the protease of Pseudomonas aeruginosa

The feasibility of a protease of Pseudomonas aeruginosa (PaproA) to prepare angiotensin I-converting enzyme (ACE) inhibitory peptides from wheat gluten was evaluated according to physiochemical and antihypertensive performances. The wheat gluten hydrolyzed by Alcalase plus PaproA (WGH_APae) to produce small fragments (<1 kDa) was particularly preferred by the superior protein recovery rate, degree of hydrolysis, ACE inhibitory potential, and stability against gastrointestinal digestion. Among the resultant fractions from WGH_APae, the lower IC50 value of fraction 7 indicated proper concentrations of proline and negatively charged amino acids were critical to modulate ionic and hydrophobic interactions on ACE catalytic sites to inhibit ACE activity. Subsequently, fraction 7 was purified to identify two successful antihypertensive peptides containing tryptophan at the carboxyl-end: SAGGYIW and APATPSFW with IC50 values of 0.002 mg/mL and 0.036 mg/mL, respectively, suggesting both peptides had potentials in the nutraceuticals and functional foods to prevent and/or treat hypertension.