Structural identification and immunomodulatory effects of chicken egg white glycopeptides

Abstract

Glycoproteins, primary proteins in egg white (EW), yield substantial EW glycopeptides (EWG) after digestion and hydrolysis. However, the structure and function of EWG have not been revealed. In this study, EWG was enriched from EW hydrolysates of simulated digestion in vitro, the structure of EWG was determined by LC-MS/MS, and their immunoregulatory effects on macrophages were investigated. The structure of EWG displayed a high degree of heterogeneity. As an example, 2 N-glycosites (N-293 and N-312), 19 peptide fragments and 45 N-glycopeptides were identified in ovalbumin. Cellular assays showed that EWG significantly increased RAW264.7 cells secretion of TNF-α (p < 0.01), indicating potent immunoactivating properties. Transcriptome sequencing analysis found that 1112 differential expression genes (DEGs) were upregulated, while 603 DEGs were downregulated in RAW264.7 cells by treatment with EWG (125 μg/mL) compared to control group. These DEGs were mainly involved in classic inflammatory signaling pathways, particularly the “TNF signaling pathway”, “NF-kappa B signaling pathway” and “MAPK signaling pathway”. Our findings provide meaningful insights for developing EWG as a potential immunoactivity ingredient and expand EW's nutritional and healthy applications.