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

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.