Purification and charicterization of angiotensin I-converting enzyme (ACE) inhibitory peptides with specific structure X-Pro

This study aimed to specifically prepare angiotensin I-converting enzyme (ACE) inhibitory peptides rich in C-terminal proline from oyster proteins using chymotrypsin and proline-specific endopeptidases (PSEases). The hydrolysates were purified with Sephadex G25, Superdex (TM) 30 Increase 10/300 GL gel filtration chromatography and reverse-phase high-performance liquid chromatography (RP-HPLC). The ACE inhibitory IC50 of purified fraction (G1E1C1) was 0.032 +/- 0.003mg/mL. According to ESI-MS and ESI-MS/MS analyses, there were three novel ACE inhibitory peptides in G1E1C1 fraction. Their sequences were Ser-Ala-Pro, Ala-Met-Pro and Thr-Ser-Gly-Pro. Molecular docking of peptides to ACE was studied. Metal-acceptor interactions and conventional hydrogen bonds greatly promoted the stability of peptides to ACE interaction. Pyrrole ring of proline may lead to higher inhibitory activity of peptides. It easily formed a Pi-alkyl interaction with aromatic ring residues (His353, His387, His513, and Phe512). Pi interactions may promote the effect of peptides on ACE. Also, C atom adjacent to the N atom of the pyrrole ring easily formed a carbon hydrogen bond with Ala354. The research discovered three novel ACE inhibitory peptides and provided a method to obtain ACE inhibitory peptides with specific structure X-Pro. The research result played an important role in revealing the structure-activity relationship of ACE inhibitory peptides and designing novel peptides with enhanced biological activity.