Purification and characterization of a novel immunomodulatory hexapeptide from alcalase hydrolysate of ultramicro-pretreated silkworm (Bombyx mori) pupa protein

Abstract Silkworm ( Bombyx mori ) pupa protein is one potential source of insect protein for use in food. Immunomodulatory peptides are specific protein fragments that can positively influence human health. Here, we purified a novel immunomodulatory hexapeptide from the alcalase hydrolysate of ultramicro-pretreated silkworm pupa proteinusing Sephadex gel filtration chromatography and reverse-phase high-performance liquid chromatography (RP-HPLC). The peptide sequence was determined by liquid chromatography–electrospray ionization– tandem mass spectrometry (LC-ESI-MS/MS). The results showed that the molecular mass of the purified peptide was 656.17 Da, and the amino acid sequence was Pro-Asn-Pro-Asn-Thr-Asn (PNPNTN). Splenocyte proliferation was 87.35% in the presence of 100 μg/ml of purified peptide. The splenocyte proliferation could be promoted upto 248.4% at 100 μg/ml of PNPNTN after induction by Concanavalin A (Con A). PNPNTN was stable in the presence of the gastrointestinal proteases pepsin and trypsin and at temperatures up to120°C. Taken together, these results show that this novel immunomodulatory hexapeptide from silkworm pupae has potential therapeutic value as an immunomodulatory component of functional food.