Glycogenolysis
Glycogenolysis is the breakdown of glycogen into glucose-derived products, chiefly glucose-1-phosphate and, at branch points, free glucose.
Glycogen phosphorylase: An enzyme that cleaves glycogen’s α-1,4-linked glucose residues by phosphorolysis, producing glucose-1-phosphate. It performs most glycogen breakdown, stopping near branch points.
Liver: A large metabolic organ that processes nutrients, detoxifies compounds, and helps regulate blood composition. Liver glycogenolysis helps maintain blood glucose between meals.
Glycogenesis: The synthesis of glycogen from glucose-derived precursors. It builds the storage polymer that glycogenolysis dismantles.
Glycogen storage disease: A group of inherited disorders caused by defects in glycogen synthesis, breakdown, or regulation. Several forms result directly from impaired glycogenolysis enzymes.
Debranching enzyme: A bifunctional enzyme that transfers glycogen residues and hydrolyzes α-1,6 branch linkages. It clears branch points that glycogen phosphorylase cannot cleave.
Skeletal muscle: Voluntary, striated muscle tissue that produces force and movement. Muscle glycogenolysis supplies glucose-derived fuel for contraction.
Glycolysis: A metabolic pathway that converts glucose or glucose-6-phosphate into pyruvate or lactate while generating ATP. Glucose-6-phosphate from glycogen can enter this energy-producing pathway.
McArdle disease: Glycogen storage disease type V, caused by deficiency of muscle glycogen phosphorylase. The defect prevents skeletal muscle from mobilizing its glycogen normally.
Glucose-1-phosphate: A phosphorylated glucose molecule formed when glycogen’s α-1,4 bonds are cleaved by phosphorylase. It is the main product released from glycogen’s linear chains.
Glucose-6-phosphatase: An enzyme that removes phosphate from glucose-6-phosphate to produce free glucose. Liver cells use it to release glycogen-derived glucose into blood; muscle lacks it.