ABSTRACT
Glycogen is stored mainly by the liver and skeletal muscle as an energy reserve. The role of stored glycogen in muscle is to provide a source of energy upon prolonged muscle contraction. Glycogen degradation requires two enzymes; glycogen phosphorylase and glycogen-debranching enzyme. Glycogen is a large polymer of glucose residues linked by α1–4 glycosidic bonds with branches every 10 residues or so via α1–6 glycosidic bonds. Glycogen phosphorylase degrades glycogen by breaking a1–4 glycosidic bonds to release glucose units one at a time from the nonreducing end of the glycogen molecule as glucose 1-phosphate. Glycogen metabolism is important because it enables the blood glucose level to be maintained between meals and also provides an energy reserve for muscular activity. The maintenance of blood glucose is essential in order to supply tissues with an easily metabolizable energy source, particularly the brain which uses only glucose except after a long starvation period.
