Identification of ace-inhibitory peptides from squid skin collagen after in vitro gastrointestinal digestion

Collagenous residues from squid skins were hydrolysed with Esperase and fractionated into three different peptide fractions (10-3 kDa, F1; 3-1 kDa, F2; <1 kDa, F3). The lowermost molecular weight fraction (F3) showed the highest ACE inhibitory capacity. The effect of simulated in vitro gastrointestinal digestion on ACE-inhibitory activity of these three peptide fractions was evaluated. For this purpose, the fractions were hydrolysed with pepsin (F1G, F2G and F3G) followed by pancreatin (F1GI, F2GI and F3GI). Pepsin digestion hardly modified the molecular weights distribution of the peptide fractions. However, digestion with pepsin followed by pancreatin gave an increase in low molecular weight peptides. The pepsin-pancreatin digestion increased the ACE-inhibitory capacity of F1 (F1GI) and especially of F3 (F3GI). A new decapeptide (Gly-Arg-Gly-Ser-Val-Pro-Ala-Hyp-Gly-Pro) with potent ACE-inhibitory capacity (IC50 47.78 mu M) was identified from the digested fraction F3GI, using liquid chromatography, isoelectric focusing and tandem mass spectrometry. The potential antihypertensive effect of the <1 kDa fraction from squid skin hydrolysate is reasonably high and could be improved after gastrointestinal digestion. (C) 2013 Elsevier Ltd. All rights reserved.