Glykosidische

Glykosidische, in English glycosidic, describes a covalent linkage formed between a sugar unit and another molecule through a glycosidic bond. This type of bond is central to the structure of disaccharides, oligosaccharides, polysaccharides, nucleosides and many glycosylated compounds. Glycosidic bonds are usually formed by a condensation reaction involving the anomeric carbon of a sugar and a hydroxyl, amino, or other nucleophile on the partner molecule, and they are hydrolyzed by acids or specific enzymes.

Glycosidic bonds are classified by the type of atom that links to the sugar and by the stereochemistry at the anomeric carbon. The main categories are O-glycosidic bonds (sugar-oxygen linkages), N-glycosidic bonds (sugar-nitrogen linkages, as in nucleosides), and, less commonly, C-glycosidic bonds (sugar-carbon linkages). The bond can be alpha or beta depending on the orientation of the anomeric substituent, which influences the properties and digestibility of the molecule. In polysaccharides, the pattern of linkages determines function: α-1,4 and α-1,6 linkages in starch and glycogen enable energy storage and branching, while β-1,4 linkages in cellulose provide structural rigidity.

In biology, glycosidic bonds connect sugars to other sugars in polysaccharides, to aglycones in glycosides, or to nitrogenous bases in nucleosides and nucleotides. Glycosidic linkages are integral to nutrition, metabolism, and cellular recognition, and are targets for enzymatic regulation as well as pharmaceutical design.