Glycogenolysis
Glycogenolysis
Glycogenolysis (pronounced: gly·co·gen·ol·y·sis) is a metabolic process that involves the breakdown of glycogen to glucose-1-phosphate and glucose, predominantly in the cells of the liver and muscles. The term is derived from the Greek words "glykys" meaning sweet, "gen" meaning become, and "lysis" meaning loosening.
Process
The process of glycogenolysis begins in the cytosol, with the release of glucose-1-phosphate from glycogen chains by the enzyme glycogen phosphorylase. This enzyme cleaves the bond linking a glucose residue to the glycogen molecule through the addition of a phosphate group. The glucose-1-phosphate is then converted to glucose-6-phosphate by the enzyme phosphoglucomutase.
In the liver, glucose-6-phosphate is further hydrolyzed to free glucose by the enzyme glucose-6-phosphatase. This glucose can then be released into the bloodstream to be used by other cells as an energy source. In the muscles, however, glucose-6-phosphate enters the glycolysis pathway directly, to be used as an immediate energy source.
Regulation
Glycogenolysis is regulated by multiple hormones, primarily glucagon and epinephrine. These hormones trigger the breakdown of glycogen into glucose when blood glucose levels are low. Conversely, when blood glucose levels are high, the hormone insulin inhibits glycogenolysis and instead promotes the storage of glucose in the form of glycogen, a process known as glycogenesis.
Clinical Significance
Abnormalities in glycogenolysis can lead to various diseases, such as McArdle's disease, a type of glycogen storage disease characterized by the inability of skeletal muscle to break down glycogen, due to the absence of the enzyme myophosphorylase.
See Also
External links
- Medical encyclopedia article on Glycogenolysis
- Wikipedia's article - Glycogenolysis
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