glykogenes

Glykogenes is the biosynthetic process that leads to the formation of glycogen, a branched polymer of glucose that serves as a storage carbohydrate in animals. In English the standard term is glycogenesis, but glykogenes is used in some European languages and in older literature. Glycogenesis occurs primarily in liver and skeletal muscle, with liver glycogen helping regulate blood glucose and muscle glycogen supplying rapid glucose during contraction.

The pathway begins with uptake of glucose and its phosphorylation to glucose-6-phosphate by hexokinase (muscle) or glucokinase (liver). Glucose-6-phosphate is isomerized to glucose-1-phosphate by phosphoglucomutase and then activated to UDP-glucose by UDP-glucose pyrophosphorylase. The core polymerization is carried out by glycogen synthase, which extends existing glycogen chains by forming α-1,4-glycosidic bonds. A branching enzyme (amylo-1,4→1,6-transglucosidase) creates α-1,6-branches, increasing compactness and solubility of the glycogen molecule.

Regulation is tight and responsive to hormone signals. Insulin promotes glycogenesis by activating protein phosphatases that dephosphorylate and activate glycogen synthase, while glucagon and epinephrine inhibit it via cAMP-dependent kinases that phosphorylate and inactivate glycogen synthase. Allosteric factors such as glucose-6-phosphate also influence enzyme activity and substrate availability.

Dysfunction in glycogenesis contributes to glycogen storage diseases, though many disorders reflect impaired glycogen breakdown or trafficking rather than synthesis alone. See also glycogen and glycogenolysis.