Glycogen storage disease type 0 liver provides a steady source of glucose from glycogen breakdown (or glycogenolysis). With prolonged fasting, glucose is generated in the liver from noncarbohydrate precursors through gluconeogenesis. Such precursors include alanine (derived from the breakdown of proteins in skeletal muscle) and glycerol (derived from the breakdown of triacylglycerols in fat cells). In patients with glycogen-storage disease type 0, fasting hypoglycemia occurs within a few hours after a meal because of the limited stores of hepatic glycogen and inadequate gluconeogenesis to maintain normoglycemia. Feeding characteristically results in postprandial hyperglycemia and glucosuria, in addition to increased blood lactate levels, because glycogen synthesis is
Glycogen synthase Glycogen synthase Glycogen synthase (UDP-glucose-glycogen glucosyltransferase) is a key enzyme in glycogenesis, the conversion of glucose into glycogen. It is a glycosyltransferase () that catalyses the reaction of UDP-glucose and (1,4-α-D-glucosyl) to yield UDP and (1,4-α-D-glucosyl). Much research has been done on glycogen degradation through studying the structure and function of glycogen phosphorylase, the key regulatory enzyme of glycogen degradation. On the other hand, much less is known about the structure of glycogen synthase, the key regulatory enzyme of glycogen synthesis. The crystal structure of glycogen synthase from "Agrobacterium tumefaciens", however, has been determined at 2.3 A resolution. In its