Glycogen phosphorylase V, McArdle's Disease). More than 65 mutations in the PYGM gene that lead to McArdle disease have been identified to date. Symptoms of McArdle disease include muscle weakness, myalgia, and lack of endurance, all stemming from low glucose levels in muscle tissue. Mutations in the liver isoform of glycogen phosphorylase (PYGL) are associated with Hers' Disease (glycogen storage disease type VI). Hers' disease is often associated with mild symptoms normally limited to hypoglycemia, and is sometimes difficult to diagnose due to residual enzyme activity. The brain isoform of glycogen phosphorylase (PYGB) has been proposed as a biomarker for gastric cancer.
Equine exertional rhabdomyolysis cell membranes may then be damaged if the horse is forced to continue work, which allows muscle enzymes and myoglobin to leak into the bloodstream. The body builds up a store of glycogen from converted carbohydrates in muscle cells. Glycogen, a fuel used by muscles for energy, is depleted during work and restocked when a horse rests. Oxygen-carrying blood metabolizes glycogen, but the blood can not flow fast enough to metabolise the excess stored glycogen. The glycogen that is not metabolized aerobically (by the oxygenated blood) must then be metabolized anaerobically, which then creates the cell waste products and heat,