Structural characterization of N‐linked oligosaccharides of laminin from rat kidney: changes during diabetes and modulation by dietary fiber and butyric acid

Carbohydrates of laminin, a family of large multidomain glycoproteins, have been implicated in various cellular activities including maintaining the protein structure, its function and also basement membrane integrity. During the course of our investigation, we observed that purified laminin from kidneys of control, diabetic, and dietary fiber- and butyric acid-treated diabetic rats showed differences in binding to extracellular matrix components. This prompted us to determine whether there are structural changes in laminin oligosaccharides. In this study, we have characterized a few major N-linked oligosaccharides isolated from purified laminin in various experimental groups, viz. normal, diabetic and diabetic rats fed with dietary fiber and butyric acid. Sugar composition, as identified by GLC, revealed the presence of mannose, galactose and N-acetylglucosamine. In order to study fine structures of the oligosaccharides, N-linked oligosaccharides of laminin were released by Peptide-N-glycosidase F digestion, end-labeled with 2-anthranilic acid and fractionated by lectin affinity chromatography. Furthermore, structural elucidation carried out by MALDI-TOF MS/MS analysis showed variations in the oligosaccharide sequence of laminin during diabetes which were altered by the feeding of dietary fiber and butyric acid.