Glykaner

Glykaner, also known as glycans, are complex carbohydrates that form polysaccharides and glycoconjugates. They range from simple chains to highly branched polymers and are found on cell surfaces, in the extracellular matrix, and in secreted fluids. Many glykaner are covalently attached to proteins or lipids, creating glycoproteins, proteoglycans and glycolipids.

Glykaner include both linear and branched structures. Major categories are N-linked glycans, attached to asparagine residues in proteins; and O-linked glycans, attached to serine or threonine residues. A distinct group, glycosaminoglycans (GAGs), are sulfated, long unbranched chains that form the core of proteoglycans in the extracellular matrix.

Monosaccharide units that build glykaner include glucose, galactose, mannose, N-acetylglucosamine, N-acetylgalactosamine, fucose, sialic acid and uronic acids. Glykaner can feature alpha or beta linkages and a range of branching patterns, contributing to extensive structural diversity and specific biological functions.

Biological roles of glykaner are diverse. They mediate cell-cell recognition and signaling, influence protein folding and stability, contribute to tissue architecture, and participate in immune modulation and host-pathogen interactions. Their composition and structure can affect developmental processes and physiological responses.

Biosynthesis occurs mainly in the endoplasmic reticulum and Golgi apparatus, guided by glycosyltransferase enzymes. N-glycans are assembled on lipid carriers and transferred to nascent proteins, while O-glycans are built directly on serine or threonine residues in the Golgi.

Clinical relevance includes congenital disorders of glycosylation and associations between abnormal glykaner structures and diseases such as cancer and inflammatory conditions. Analytical methods such as mass spectrometry, chromatography and nuclear magnetic resonance are used to study glykaner, and resources like glycan databases catalog their structures and functions.