Glycogen storage disease type I as fat. When digestion of a meal is complete, insulin levels fall, and enzyme systems in the liver cells begin to remove glucose molecules from strands of glycogen in the form of G6P. This process is termed glycogenolysis. The G6P remains within the liver cell unless the phosphate is cleaved by glucose-6-phosphatase. This dephosphorylation reaction produces free glucose and free anions. The free glucose molecules can be transported out of the liver cells into the blood to maintain an adequate supply of glucose to the brain and other organs of the body. Glycogenolysis can supply the glucose needs of an
Glycogen synthase regulating glycogen/glucose levels and is activated by dephosphorylation. In humans, there are two paralogous isozymes of glycogen synthase: The liver enzyme expression is restricted to the liver, whereas the muscle enzyme is widely expressed. Liver glycogen serves as a storage pool to maintain the blood glucose level during fasting, whereas muscle glycogen synthesis accounts for disposal of up to 90% of ingested glucose. The role of muscle glycogen is as a reserve to provide energy during bursts of activity. Meanwhile, the muscle isozyme plays a major role in the cellular response to long-term adaptation to hypoxia. Notably, hypoxia only induces