Two Antihypertensive and Antioxidant Peptides Derived from Alaska Pollack (Theragra chalcograma) Skin: <i>In Silico</i>, <i>In Vitro</i>, and <i>In Vivo</i> 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.