60Co-γ-ray-irradiated edible silkworm (Bombyx mori) pupae-assisted protease digestion: A strategy for obtaining low molecular weight bioactive peptides

Bioactive peptides from edible insect protein are a class of peptide compounds with relatively low molecular weight, possessing specific biological activity functions, but their extraction and utilization face challenges. The study aims to explore a novel approach using ⁶⁰Co-γ-ray irradiation-assisted enzymatic hydrolysis of silkworm pupae protein to obtain bioactive peptides. The silkworm pupae were irradiated with ⁶⁰Co-γ-ray at a dose point of 10 kGy, and then the protein was extracted and subsequently hydrolyzed by alkaline protease, and the irradiated silkworm pupae protein improved solubility and hydrolysis degree. The proportion of α-helix in the secondary structure of the irradiated silkworm pupae protein increases, indicating that irradiation can enhance its functional properties by altering the intrinsic structure. Through irradiation-assisted enzymatic hydrolysis, The percentage of low molecular weight peptides (180–500 Da) prepared by irradiation-coupled enzymatic hydrolysis increased from 32.04 ± 0.97% to 52.77 ± 0.72%, and the percentage of low molecular weight peptides (0.5–1 kDa) increased from 19.65 ± 0.52% to 24.75 ± 0.79%. Activity-guided isolation and identification reveal a greater diversity of peptides with antioxidant, hypoglycemic, and hypotensive activities in the irradiated group, including novel peptides such as QASSGTPATLR, LLPR, FKVPN, and HHFP that exhibit strong scavenging activity against DPPH radicals, α-glucosidase inhibition, Fe²⁺ chelation, and angiotensin-converting enzyme (ACE) inhibition. Molecular docking simulations shown that the irradiated peptides have enhanced affinity for target enzymes, suggesting that the ⁶⁰Co-γ-ray irradiation-assisted enzymatic hydrolysis technique can effectively improve peptide activity. This study provides a theoretical basis for irradiation-assisted enzymatic degradation of edible insect proteins to obtain low molecular weight bioactive peptides.