Identification and mechanistic study of four novel ACE inhibitory peptides from maize germ protein hydrolysates

Nowadays, much exertion has been given to identifying angiotensin-I converting enzyme inhibitory peptides (ACEIPs) from food by-products, while little attention has been paid to exploiting the potential use of maize germ proteins. Here, we identified four novel ACEIPs -PW, VTLL, LPGP, and SPGTAF, from maize germ protein hydrolysates. Inhibition assay demonstrated that these four peptides suppressed ACE activity with high potencies. Kinetics studies showed that PW inhibited ACE in a non-competitive manner with a Km of 1.15 mmol/L, whereas VTLL, LPGP, and SPGTAF were ACE substrate-competitive inhibitors with a constant Vmax of 0.005 △345 nm/min. Furthermore, molecular docking proved that PW mainly interacted with the key residues in the hydrophobic pocket of ACE through hydrogen bonding. Meanwhile, VTLL, LPGP, and SPGTAF docked at the catalytic domain of ACE and stabilized by hydrogen bonding with residues that coordinated Zn (II) or substrates. Our study suggests that the by-add product of maize could function as an alternative source for generating ACEIPs.