Antidiabetic Potential of Chinese Giant Salamander (Andrias davidianus)-Derived Peptide: Isolation and Characterization of DPP4 Inhibitory Peptides

Amid the global rise in type 2 diabetes, natural peptide-based therapies provide a safer alternative to synthetic drugs with fewer side effects. This study highlights the antidiabetic potential of peptides derived from cultured Chinese giant salamander (CGS) meat hydrolyzed by Alcalase 2.4L FG through DPP4 inhibitory activity. The hydrolysate exhibited significant DPP4 inhibitory activity, with an IC50 value of 1317.0 ± 29.5 μg/mL. Using activity-guided modified-SPE fractionation, the most potent DPP4 inhibitory peptide, PPAAQLL (PL7), was identified from CGS alcalase hydrolysate, with an IC50 of 230.1 ± 4.9 μM. PL7 was identified as a non-competitive inhibitor through enzyme kinetic studies, and intermolecular docking simulations suggested that it does not interact with the active site of DPP4. Additionally, PL7’s stability against DPP4 and simulated gastrointestinal protease digestion suggested that its inhibitory activity remains intact, indicating potential for effective oral administration. SRM quantification analysis revealed nearly a six-fold enrichment of PL7 in the RP-SPE fraction S1 compared to the crude hydrolysate, underscoring the effectiveness of the fractionation method. These findings highlight CGS alcalase hydrolysate as a promising source of DPP4 inhibitory peptides for managing type 2 diabetes. Future studies should focus on the in vivo efficacy, bioavailability, and pharmacokinetics of PL7.