glycosaminoglycansheparin

Glycosaminoglycans (GAGs) are a family of long, linear, sulfated polysaccharides that are negatively charged due to sulfate and carboxylate groups. They occur primarily as components of proteoglycans in the extracellular matrix and on cell surfaces, where they contribute to hydration, resilience, and signaling. GAGs share a repeating disaccharide unit and vary in the types of uronic acid and amino sugar, as well as in sulfation patterns. The major classes include hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate, heparan sulfate, and heparin. Hyaluronic acid is unique in being non-sulfated and not covalently attached to a protein.

Heparin is a highly sulfated member of the GAG family. It is produced mainly by mast cells in mammals and stored in secretory granules. Heparin is best known for its clinical use as an anticoagulant. It acts by binding to antithrombin III, enhancing its inhibition of thrombin (factor IIa) and factor Xa, thereby preventing clot formation. Clinically, unfractionated heparin and low-molecular-weight heparins are used to prevent and treat thrombosis, during procedures, and in various surgical settings. Heparin therapy requires monitoring for bleeding risk and can be associated with adverse effects, including heparin-induced thrombocytopenia.

GAGs are synthesized in the Golgi as proteoglycan core proteins or free chains and are degraded by specific lysosomal enzymes. Their diverse sulfation patterns and interactions with water and cations give them structural and regulatory roles in tissue development, wound healing, coagulation, and cell signaling, as well as lubrication in joints (notably hyaluronic acid).