title: N-glycosylation of ovomucin from hen egg white.
abstract: Ovomucin is a bioactive egg white glycoprotein responsible for the gel properties of fresh egg white and is believed to be involved in egg white thinning, a natural process that occurs during storage. Ovomucin is composed of two subunits: a carbohydrate-rich β-ovomucin with molecular weight of 400-610 KDa and a carbohydrate-poor α-ovomucin with molecular mass of 254 KDa. In addition to limited information on O-linked glycans of ovomucin, there is no study on either the N-glycan structures or the N-glycosylation sites. The purpose of the present study was to characterize the N-glycosylation of ovomucin from fresh eggs using nano LC ESI-MS, MS/MS and MALDI MS. Our results showed the presence of N-linked glycans on both glycoproteins. We found 18 potential N-glycosylation sites in α-ovomucin. 15 sites were glycosylated, one site was found in both glycosylated and non-glycosylated forms and two potential glycosylation sites were found unoccupied. The N-glycans of α-ovomucin found on the glycosylation sites are complex-type structures with bisecting N-acetylglucosamine. MALDI MS of the N-glycans released from α-ovomucin by PNGase F revealed that the most abundant glycan structure is a bisected type of composition GlcNAc(6)Man(3). Two N-glycosylated sites were found in β-ovomucin.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, 4-10 Ag/For Centre, Edmonton, Alberta, T6G 2P5, Canada.
authors.forename: Marina
authors.initials: M
authors.lastname: Offengenden
authors.forename: Messele A
authors.initials: MA
authors.lastname: Fentabil
authors.forename: Jianping
authors.initials: J
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D002853:Chromatography, Liquid; D004529:Egg White / Q000737:chemistry*; D006031:Glycosylation; D008969:Molecular Sequence Data; D010059:Ovomucin / Q000737:chemistry*; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D010059:Ovomucin; D043524:Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase