glükosiidside

Glükosiidside, known in English as the glycosidic bond, is the covalent linkage that connects a carbohydrate molecule to another group, which may be a second sugar or a non-carbohydrate moiety. The bond forms by a dehydration reaction between the anomeric carbon of a sugar and a hydroxyl or amino group of the partner molecule.

Glycosidic bonds are classified as O-glycosidic (through oxygen) or N-glycosidic (through nitrogen). The bond can be described as alpha or beta depending on the configuration at the anomeric carbon. In disaccharides, the linkage is defined by donor and acceptor units (for example, maltose has an α-1,4 linkage). In nucleosides, the glycosidic bond connects the sugar to a nitrogenous base (an N-glycosidic bond).

Glycosidic bonds can be hydrolyzed by acids or by glycosidase enzymes. Enzymes such as maltase or sucrase cleave specific glycosidic linkages during digestion, while acid hydrolysis can occur under strong conditions. The chemistry of these bonds also governs the reducing properties of sugars; a free anomeric carbon renders a sugar reducing, whereas a glycosidic bond at the anomeric position can render it non-reducing.

Biologically, glycosidic bonds enable diverse roles: they form storage polysaccharides like starch and glycogen, structural polysaccharides like cellulose (different linkage types), and they link sugars to proteins and lipids in glycoproteins and glycolipids, influencing folding, stability, recognition, and signaling.