The enzyme (EC 188.8.131.52) that catalyses the sequential removal of glycosyl residues from unbranched glycogen, producing glucose 1-phosphate. Activity is regulated allosterically and by phosphorylase kinase.There are tissue-specific isozymes in muscle (GPMM, 842 aa), liver (GPLL, 847 aa) and brain (GPBB, 862 aa). GPMM is released from cardiac muscle following ischaemia and is a marker for acute myocardial infarction. Mutations in the liver enzyme lead to glycogen storage disease VI (Hers' disease), in the muscle enzyme to McArdle's disease.
Subjects: Medicine and Health — Chemistry.