Structural characterization and functional study of Lycium barbarum glycoprotein LbGp-f2 based on glycoproteomics

Lycium barbarum polysaccharides (LBPs) are among the major bioactive constituents of Goji berries. Increasing evidence indicates that LBPs are not homogeneous polysaccharides but rather complex systems composed of polysaccharide-protein complexes and glycoproteins. Among these components, Lycium barbarum glycoprotein (LbGp) has attracted growing attention because glycosylation modifications may strongly influence its structural properties and biological activities. In the present study, a glycoprotein fraction, LbGp-f2, was isolated from "Ningqi No.1" Goji and systematically characterized using glycoproteomics approaches. Structural analyses revealed its molecular weight, purity, protein and sugar contents, and amino acid composition. Combined label-free intact glycopeptide analysis and HPLC-MS/MS identified 20 N-glycoproteins and 10 O-glycoproteins, including several glycosidase-related proteins such as α-galactosidase, β-glucosidase, and 1,4-β-xylosidase. GO and KEGG enrichment analyses demonstrated that LbGp-f2 is closely associated with cell wall polysaccharide metabolism, xylan degradation, galactose metabolism, and sphingolipid-related metabolic pathways, suggesting potential roles in fruit cell wall remodeling and energy metabolism during fruit development. These findings provide new molecular evidence supporting the structure-function relationship of Lycium barbarum glycoproteins and contribute to a deeper understanding of glycoprotein-mediated metabolic regulation within the Lycium barbarum polysaccharide system.