Glycogen phosphorylase that regulates glycogen mobilization (PubMed:27402852). Phosphorylase is an important allosteric enzyme in carbohydrate metabolism (PubMed:3346228). Enzymes from different sources differ in their regulatory mechanisms and in their natural substrates (PubMed:3346228). However, all known phosphorylases share catalytic and structural properties (PubMed:3346228). [(1->4)-alpha-D-glucosyl](n) + phosphate = [(1->4)-alpha-D-glucosyl](n-1) + alpha-D-glucose 1-phosphate Activity of phosphorylase is controlled both by allosteric means (through the non-covalent binding of metabolites) and by covalent modification. Thus AMP allosterically activates, whereas ATP, ADP, and glucose-6-phosphate allosterically inhibit, phosphorylase B. Activated upon phosphorylation. Homodimer. Dimers associate into a tetramer to form the enzymatically active phosphorylase A. Phosphorylated (PubMed:27402852). Phosphorylation of Ser-15 converts phosphorylase B (unphosphorylated) to phosphorylase A (By similarity). Belongs to the glycogen phosphorylase family.