Phosphorylase is an important allosteric enzyme in carbohydrate metabolism. Enzymes from different sources differ in their regulatory mechanisms and in their natural substrates. However, all known phosphorylases share catalytic and structural properties. [(1->4)-alpha-D-glucosyl](n) + phosphate = [(1->4)-alpha-D-glucosyl](n-1) + alpha-D-glucose 1-phosphate Homodimer. Appears during cell differentiation; absent in amoebae and early stages of development, reaches a maximum level of expression at the slug stage and then decreases. The N-terminus is blocked. Enzyme activity requires processing of the 113 kDa peptide to an enzymatically active 106 kDa form of the protein. Processing would occur near the middle of the Gln-rich repetitive element. In D.discoideum glycogen phosphorylase exists as 2 developmentally regulated forms, GP1 and GP2, which are the products of separate genes. Belongs to the glycogen phosphorylase family.