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 (By similarity). May be not required for the degradation of starch, but the phosphorolysis of starch may play an important role in water stress tolerance. [(1->4)-alpha-D-glucosyl](n) + phosphate = [(1->4)-alpha-D-glucosyl](n-1) + alpha-D-glucose 1-phosphate Small white lesions on the tips or margins of fully expanded leaves. Belongs to the glycogen phosphorylase family.