Novel strategy to improve the bioactivity and anti-hydrolysis ability of oat peptides via zinc ion-induced assembling

This study aims to use metal ion coordinating method to improve the bioactivity and anti-hydrolysis ability of bioactive peptides. We demonstrated that zinc (Zn) coordination (10:1 mass ratio of peptide to Zn, pH 6.8, 37 °C) induced assembly of oat peptides, improved pancreatic lipase (PL) inhibitory activity by 30.4-36.8 % and anti-hydrolysis ability against intestinal proteases by 26.5-38.2 %; meanwhile, the peptide-Zn complex drastically reduced the PL affinity to the substrate. Detailed mechanism analysis showed that the high hydrophobicity (276 of fluorescent intensity) and dense eutectic structure of peptide-Zn complexes caused the hard hydrolysis of complexed peptides by proteases; in particular, the neutralized surface charges (∼-3.6 mV) of complexes imparted the peptide-Zn complex high affinity towards PL (-22.3 mV) thus robust PL inhibitory activity. These findings deepened our understanding of the interaction of peptides with metal elements and set the groundwork for the enhancement and protection of bioactive peptides.