Glycogen debranching enzyme and progressive muscle involvement, with variations caused by age of onset, rate of disease progression and severity. Patients with Type IIIb generally symptoms related to liver disease. Type III patients be distinguished by elevated liver enzymes, with normal uric acid and blood lactate levels, differing from other forms of GSD. In patients with muscle involvement, Type IIIa, the muscle weakness becomes predominant into adulthood and can lead to ventricular hypertrophy and distal muscle wasting. 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,
Glycogen phosphorylase Glycogen phosphorylase is regulated by both allosteric control and by phosphorylation. Hormones such as epinephrine, insulin and glucagon regulate glycogen phosphorylase using second messenger amplification systems that are linked to G proteins. Glucagon activates adenylate cyclase through a seven transmembrane receptor coupled to G which, in turn, activates adenylate cyclase to increase intracellular concentrations of cAMP. cAMP binds to and releases an active form of protein kinase A (PKA). Next, PKA phosphorylates phosphorylase kinase, which, in turn, phosphorylates glycogen phosphorylase b, transforming it into the active glycogen phosphorylase a. This phosphorylation is added onto the glycogen phosphorylase b serine 14.