Phophorylases are important allosteric enzymes in the 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. For example glycogen phosphorylase catalyses the intracellular degradation of glycogen into glucose-1-phosphate, the first step of glycolysis. It was the first enzyme to be discovered that was controlled by phosphorylation. Other phosphorylases include maltodextrin phosphorylase and starch phosphorylase.