Studies on glycosaminoglycan structure and interaction with proteins and enzymes

Over the last few decades, glycosaminoglycans like heparin and heparan sulfate have been shown to interact with a number of biologically important proteins, thereby playing an essential role in the regulation of various physiological processes. These interactions have a high degree of specificity in most cases. Thus, there is a need to characterize the molecular properties within glycosaminoglycans and proteins that are responsible for specific recognition. The enzymatic degradation of glycosaminoglycans is also recognized as an important analytical and therapeutic tool for determining the fine structure of glycosaminoglycans and neutralizing their physiological effects in vivo.; The focus of the current work was to study structural and functional aspects of glycosaminoglycan interaction with physiologically important proteins and also to evaluate enzymatic mechanisms for glycosaminoglycan degradation. The structure-function relationship of the interaction of heparin with fibroblast growth factor-2 (FGF-2) was studied by chemical modification of a related glycosaminoglycan, acharan sulfate. The relative importance of the 2- and 6-O-sulfo groups in heparin for FGF-2 binding and activation was evaluated.; While the interaction of heparin with various families of proteins has been extensively studied, less is known about heparin interaction with lipid or membrane-binding proteins. The energetics and kinetics of the interaction of heparin with two biologically important lipid-binding proteins (annexin V and apolipoprotein E4) was studied and the minimum oligosaccharide sequence within heparin required for specific binding was determined. Based on these studies a model for interaction of heparin with these lipid-binding proteins is proposed.; Mechanisms for glycosaminglycan degradation were studied by evaluating the action of chondroitin AC lyase (from Flavobacterium heparinum ) on chondroitin-6-sulfate. Results were compared with similar data obtained for a mutant of this enzyme and the implications of structural changes in the enzyme on its action pattern for the same substrate are studied. Conformational studies on Δ4-uronate residues, which occur at the non-reducing end of oligosaccharides prepared by lyase treatment, were also carried out to determine what factors influence the equilibrium between the conformers. These studies provide a better understanding of various aspects of glycosaminoglycan-protein interaction.