Glycogenesis

Glycogenesis is the process of glycogen synthesis, in which glucose molecules are added to chains of glycogen for storage. This process is activated during rest periods following the Cori cycle, in the liver, and also activated by insulin in response to high glucose levels.

Process

Glycogenesis starts with a molecule of glucose 6-phosphate, which is converted to glucose 1-phosphate by the enzyme phosphoglucomutase. This glucose molecule is then attached to a glycogenin starter molecule by a glycosidic bond, catalyzed by the enzyme glycogen synthase.

The addition of glucose molecules to the chain involves the creation of alpha 1,4-glycosidic bonds, catalyzed by the enzyme glycogen synthase. Branches are created by the enzyme branching enzyme, which moves a block of oligoglucose from one chain and adds it to the growing glycogen molecule through an alpha 1,6-glycosidic bond.

Regulation

Glycogenesis is regulated by many hormones, including insulin, glucagon, and epinephrine. Insulin promotes glycogenesis by activating glycogen synthase and inhibiting glycogen phosphorylase. Glucagon and epinephrine have the opposite effect, inhibiting glycogen synthase and activating glycogen phosphorylase, thus promoting glycogenolysis.

Clinical significance

Defects in glycogenesis can lead to glycogen storage diseases, a group of genetic disorders that result from a deficiency in one of the enzymes necessary for either glycogen synthesis or breakdown.

See also

• Glycogenolysis
• Gluconeogenesis
• Cori cycle
• Glycogen storage diseases

References

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  Glycogenesis

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  Metabolism of common monosaccharides, and related reactions