heteropolysaccharide

A heteropolysaccharide is a polysaccharide composed of two or more different monosaccharide types in its chain, unlike a homopolysaccharide that contains only a single monosaccharide. The monosaccharide units can form repeating disaccharide or longer sequences and may be arranged linearly or in branched architectures.

Many heteropolysaccharides are glycosaminoglycans (GAGs), highly acidic and sulfated polymers that occur mainly in animals. Common examples include hyaluronic acid (repeating disaccharide of glucuronic acid and N-acetylglucosamine, non-sulfated), chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate. Their diverse sulfation and acetylation patterns give rise to a range of charges and biological interactions.

Biological roles: Heteropolysaccharides are major components of the extracellular matrix and cell surfaces. They often exist as proteoglycans, where the polysaccharide chains are covalently attached to core proteins. They contribute to tissue hydration, lubrication of joints, and regulation of cell signaling by binding growth factors and enzymes.

Synthesis and properties: In cells, heteropolysaccharide chains are assembled in the Golgi apparatus by glycosyltransferases, then exported. They are typically large, polydisperse, and highly heterogeneous, with property differences due to the pattern of monosaccharide composition and substitution.

Applications and relevance: Because of their biological roles, heteropolysaccharides have medical and industrial relevance. For example, heparin is a highly sulfated heteropolysaccharide used as an anticoagulant; hyaluronic acid is used in ophthalmology and cosmetic applications.