Revalorisation of bovine collagen as a potential precursor of angiotensin I-converting enzyme (ACE) inhibitory peptides based on in silico and in vitro protein digestions

• In silico proteolysis of bovine collagen released many ACE-inhibitory peptide sequences.
• The ACE-inhibitory activities of in silico-derived peptides were predicted by QSAR models.
• In silico peptides (YW and LRY) were experimentally verified as novel ACE inhibitors.
• In vitro papain-catalysed digestion of bovine collagen also released ACE-inhibitory peptides.

In silico proteolysis using 27 proteases theoretically released numerous ACE-inhibitory peptides from collagen alpha-1(I) and alpha-2(I) sequences. Papain was the most effective protease to release ACE-inhibitory peptides. Two quantitative structure–activity relationship (QSAR) models for ACE-inhibitory peptides were established and employed to predict the activities of in silico-derived collagen peptides. Furthermore, two promising in silico peptides (Tyr-Trp and Leu-Arg-Tyr) derived from papain and bromelain digestion were synthesised and experimentally confirmed as novel ACE inhibitors. In vitro digestion of collagen by papain generated ACE-inhibitory peptides and the most active one was identified as a pentapeptide (Gly-Pro-Arg-Gly-Phe). However, Gly-Pro-Arg-Gly-Phe remained unidentified as the ACE-inhibitory peptide during the in silico digestion by papain mainly due to complete hydrolysis, which was not the case during in vitro digestion affected by external factors. Overall, the present study highlights bovine collagen as a promising precursor of ACE-inhibitory peptides by in silico and in vitro protein digestions.