Abstract: To prepare dipeptidyl peptidase-IV (DPP-IV) inhibitory peptides, Pacific oyster flesh (Crassostrea gigas) was hydrolyzed with five different proteases, including papain, alcalase, pancreatin, neutrase and protromex. The pancreatin hydrolysate was found to have higher DPP-IV inhibitory activity as compared with the other four hydrolysates. The optimal hydrolysis conditions with pancreatin were determined to be 0.8%, 8.0, 37 ℃ and 90 min for enzyme dosage, pH, temperature, and hydrolysis duration, respectively. The hydrolysate obtained using the optimized conditions was purified and fractionated sequentially by ultrafiltration, Sephadex G-15 column chromatography and high performance liquid chromatography (HPLC) into different peptide fractions. Two DPP-IV inhibitory peptides were obtained and identified as Glu-Ile-Thr-Ala-Leu-Ala-Pro-Ser-Thr-Met-Lys (EITALAPSTMK) and Ile-Leu-Ala-Pro-Pro-Glu-Arg (ILAPPER) by mass spectrometry (MS). Their digestibility characteristics in gastrointestinal fluid were analyzed using online simulation with BIOPEP. Two peptides APSTM and ILAPPER were synthesized by solid-phase synthesis for DPP-IV inhibitory activity evaluation. The results showed that the half-maximal inhibitory concentration (IC50) values of the two peptides were 354.81 and 16.98 mmol/L, respectively. Molecular docking results indicated that inhibitory peptides interacted with the active site of DPP-IV through hydrogen bonds, van der Waals forces and p bonds. The results of this study provide a theoretical basis for the development of functional foods from oyster in the future.

Key words: oyster; dipeptidyl peptidase-IV inhibitory peptide; isolation and purification; inhibitory activity; molecular docking