Glycogen phosphorylase concentration, as the liver acts as a glucose exporter. In essence, liver phosphorylase is responsive to glucose, which causes a very responsive transition from the R to T form, inactivating it; furthermore, liver phosphorylase is insensitive to AMP. Glycogen phosphorylase was the first allosteric enzyme to be discovered. This accomplishment was one of many landmark achievements made by Carl and Gerty Cori. In 1943, with the help of Arda Green, the pair illustrated that glycogen phosphorylase existed in either the or b forms depending on its phosphorylation state, as well as in the R or T states based on the
Glycogen branching enzyme position to which they are transferred, the enzyme creates the very characteristic, highly branched glycogen molecule. Mutations in this gene are associated with glycogen storage disease type IV (also known as Andersen's disease) in newborns and with adult polyglucosan body disease. Approximately 40 mutations in the GBE1 gene, most resulting in a point mutation in the glycogen branching enzyme, have led to the early childhood disorder, glycogen storage disease type IV (GSD IV). This disease is characterized by a severe depletion or complete absence of GBE, resulting in the accumulation of abnormally structured glycogen, known as polyglucosan bodies. Glycogen buildup