Identification of N-Glycosites in Chicken Egg White Proteins Using an Omics Strategy.

Chicken egg white (CEW) is a perfect source of natural proteins that possesses outstanding functional properties and various bioactivities. The glycosylation structure of CEW proteins plays important roles in their functions, bioactivities, and allergies. The present work attempted to identify N-glycosites of CEW proteins using an omics strategy. CEW proteins were digested with trypsin and chymotrypsin; glycopeptides were enriched and deglycosylated using PNGase F in H2(18)O water, followed by analysis using high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS). A total of 71 N-glycosites in 26 CEW glycoproteins were identified. Web-Logo analysis showed that most of the N-glycosites were at N-X-T (55%) and N-X-S (32%). Furthermore, two-dimensional electrophoresis of CEW clusterin demonstrated a series of spots horizontally distributed at 35-37 kDa with an extremely wide isoelectric point range of 4.54-6.68, indicating the heterogeneity of glycosylation of CEW clusterin. These results provided important information for the understanding of the structures, functions, and bioactivities of CEW glycoproteins.