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Glycogenesis is the process of glycogen synthesis or the process of converting glucose into glycogen 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 .
Glycogenolysis is the breakdown of glycogen (n) to glucose-1-phosphate and glycogen (n-1). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis , by the enzyme glycogen phosphorylase .
The catalytic site is found on the lumenal face of the membrane, and removes the phosphate group from glucose 6-phosphate produced during glycogenolysis or gluconeogenesis. Free glucose is transported out of the endoplasmic reticulum via GLUT7 and released into the bloodstream via GLUT2 for uptake by other cells. Muscle cells lack this enzyme ...
Conversely, glycogenesis is enhanced and glycogenolysis inhibited when there are high levels of insulin in the blood. [ 15 ] The level of circulatory glucose (known informally as "blood sugar"), as well as the detection of nutrients in the Duodenum is the most important factor determining the amount of glucagon or insulin produced.
Glycogen synthase (UDP-glucose-glycogen glucosyltransferase) is a key enzyme in glycogenesis, the conversion of glucose into glycogen. It is a glycosyltransferase (EC 2.4.1.11) that catalyses the reaction of UDP-glucose and (1,4-α-D-glucosyl) n to yield UDP and (1,4-α-D-glucosyl) n+1.
Glycogen phosphorylase catalyzes the rate-limiting step in glycogenolysis in animals by releasing glucose-1-phosphate from the terminal alpha-1,4-glycosidic bond. Glycogen phosphorylase is also studied as a model protein regulated by both reversible phosphorylation and allosteric effects.
The official name for the gene is "amylo-α-1,6-glucosidase, 4-α-glucanotransferase", with the official symbol AGL. AGL is an autosomal gene found on chromosome 1p21. [11] The AGL gene provides instructions for making several different versions, known as isoforms, of the glycogen debranching enzyme.
As it affects glycogenolysis, it has been suggested that it should re-designated as GSD-XIV. [3] Lafora disease is considered a complex neurodegenerative disease and also a glycogen metabolism disorder. [40] Polyglucosan storage myopathies are associated with defective glycogen metabolism [41]