European Carp (Cyprinus carpio L.) Protein-Derived Ex Vivo Digests and In Vitro Hydrolysates Differ in the ACE I Inhibitory Activity and Composition of Released ACE Inhibitory Peptides.

Carp muscle tissue is a valuable source of biologically active constituents known to positively influence human health. In this study, carp protein digests/hydrolysates generated by human/ porcine digestive enzymes were analysed for their angiotensin I-converting enzyme inhibitory (ACEi) activity. The ex vivo digests and in vitro hydrolysates were used in a screening for ACEi peptides as well. Carp proteins were hydrolysed more rapidly by human gastrointestinal juices than by porcine enzymes. Sarcoplasmic protein fractions were digested/hydrolysed more easily than the myofibrillar ones. The inhibitory concentrations at 50% (IC50) for ex vivo digested sarcoplasmic and myofibrillar protein fractions were established at 1.50 and 1.04 mg/mL, respectively. While, for in vitro hydrolysed sarcoplasmic and myofibrillar protein fractions, the IC50 values were calculated as 2.57 and 1.12 mg/mL, respectively. The digested/hydrolysed samples of carp sarcoplasmic and myofibrillar protein fractions were separated by RP-HPLC-MS. Amino acid sequences were identified with the use of the LC-MS/MS method coupled with in silico systematic screening for ACEi peptides. ACEi peptides with IVY, IY, VY, ALPHA and VKAGF sequences were found in the carp digests/hydrolysates. In the ex vivo carp digest, an ACEi peptide TVY was also detected, while the ACEi peptide IW was identified in in vitro hydrolysate. Our study showed that different ACEi effects of carp digests and hydrolysates were generated with the use of human gastrointestinal and porcine enzymes.