Glycogen debranching enzyme Glycogen debranching enzyme A debranching enzyme is a molecule that helps facilitate the breakdown of glycogen, which serves as a store of glucose in the body, through glucosyltransferase and glucosidase activity. Together with phosphorylases, debranching enzymes mobilize glucose reserves from glycogen deposits in the muscles and liver. This constitutes a major source of energy reserves in most organisms. Glycogen breakdown is highly regulated in the body, especially in the liver, by various hormones including insulin and glucagon, to maintain a homeostatic balance of blood-glucose levels. When glycogen breakdown is compromised by mutations in the glycogen debranching enzyme, metabolic diseases such
PYGL glycolysis and other biosynthetic functions for energy metabolism. As the major isozyme in liver, PYGL is responsible for maintaining blood glucose homeostasis by regulating the release of glucose 1-phosphate from liver glycogen stores. One model suggests that Ca oscillations play a role in activating glycogen phosphorylase in glycogen degradation in liver cells. Through its function in the liver, PYGL is also central to meeting the glycemic demands of the entire body. Though other tissues may express all three forms in different proportions, the purpose of expressing multiple glycogen phosphorylases remains unclear. PYGL has been implicated in glycogen storage disease type