Two Antihypertensive and Antioxidant Peptides Derived from Alaska Pollack (Theragra chalcograma) Skin: In Silico, In Vitro, and In Vivo Investigation

This study aimed to identify and characterize two novel dual-functional peptides with antihypertensive and antioxidant activities from byproducts of Alaska pollock skin (APS). Results showed that fifty-nine peptides were identified from APS, of which two peptides, GP1 (GSAGPAGPSGPRGP) and GP2 (LGDARNSPAPP), were predicted to exhibit the highest angiotensin-converting enzyme (ACE) inhibitory and antioxidant activities. GP1 and GP2 demonstrated favorable ACE inhibitory activities (IC50 values of 0.166 and 0.177 mmol/L, respectively) and significantly reduced blood pressure in hypertensive rats. Additionally, both peptides effectively scavenged 2,2'-casino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, with EC50 values of 0.273 and 0.629 mg/mL and protected HepG2 cells against H2O2-induced damage. Molecular docking revealed that the peptides interacted with amino acid residues within the active pocket and at the entrance channel of ACE, displaying mixed-competitive inhibition patterns. These peptides could also bind to the Kelch domain of Kelch-like ECH associating protein (Keap1), thereby promoting nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated transcriptional activation of antioxidant enzymes through the Keap1-Nrf2 pathway. The dual ACE inhibitory and antioxidant properties of APS peptides, coupled with high gastrointestinal stability, validated their utilization as multifunctional ingredients in antihypertensive functional foods, nutraceuticals, and peptide-based hydrogel development.