A new strategy for identification of N-glycosylated proteins and unambiguous assignment of their glycosylation sites using HILIC enrichment and partial deglycosylation.

Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
Journal of Proteome Research (Impact Factor: 5). 06/2004; 3(3):556-66. DOI: 10.1021/pr034112b
Source: PubMed

ABSTRACT Characterization of glycoproteins using mass spectrometry ranges from determination of carbohydrate-protein linkages to the full characterization of all glycan structures attached to each glycosylation site. In a novel approach to identify N-glycosylation sites in complex biological samples, we performed an enrichment of glycosylated peptides through hydrophilic interaction liquid chromatography (HILIC) followed by partial deglycosylation using a combination of endo-beta-N-acetylglucosaminidases (EC After hydrolysis with these enzymes, a single N-acetylglucosamine (GlcNAc) residue remains linked to the asparagine residue. The removal of the major part of the glycan simplifies the MS/MS fragment ion spectra of glycopeptides, while the remaining GlcNAc residue enables unambiguous assignment of the glycosylation site together with the amino acid sequence. We first tested our approach on a mixture of known glycoproteins, and subsequently the method was applied to samples of human plasma obtained by lectin chromatography followed by 1D gel-electrophoresis for determination of 62 glycosylation sites in 37 glycoproteins.

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