ABSTRACT
I. INTRODUCTION In recent years, much attention has been paid to the chemistry and biochemistry of carbohydrates due to their many functions both inside and outside living cells. The glycosaminoglycans (GAGs) are related linear, polydisperse, microheterogeneous polyanionic polysaccharides. The most common GAGs are heparin, heparan sulfate, hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratan sulfate. The GAGs are generally believed to exert their biological activities through the localization, stabilization, activation, or inactivation of interacting proteins (1). These interactions play important roles in the normal physiology of animals (2) and are also involved in certain pathological processes (3). Heparin, the most studied GAG, is unique in its intracellular location in mast cell and basophil granules. Exogenous heparin is regularly used as an anticoagulant/antithrombotic agent to maintain blood flow in the vasculature through the binding and activation of antithrombin III (ATIII, a coagulation serine protease inhibitor, SERPIN) (1). Heparin has been found to bind a wide range of proteins (1,4), and it regulates a number of important biological activities. Heparan sulfate, structurally similar to heparin, is localized on the external surface of cell membranes and in the extracellular matrix and plays a major role in cell-cell and cell-protein interaction (1). Heparan sulfate (not heparin) is also believed to be an endogenous receptor for circulating growth factors and chemokines that reg-
ulate cell growth and migration (1). Other GAGs also bind proteins, but the interactions are generally less well studied than those of heparin and heparan sulfate. In addition to GAGs there are a number of synthetic, semisynthetic, and natural GAG analogues that are of medicinal interest (1). An understanding of how these GAGs and GAG analogues interact with proteins is needed to develop either carbohydrate-based, peptide-based, or synthetic therapeutics for the prevention and treatment of disease processes, including control of coagulation (1) and the control of tumor cell replication, migration, invasion, and vascularization (2,3). In this chapter, the structures and therapeutic potential of these important GAGs, GAG-binding proteins, and the quantitative methods for characterization of polysaccharide-protein binding interactions will be provided as a background. Recent advances in the application of affinity capillary electrophoresis (ACE) to study these specific interactions will be discussed.
