Pullulanase is an enzyme that catalyzes the hydrolysis of pullulan, a polysaccharide made up of glucose molecules linked by α-1,6-glycosidic bonds. The function of pullulanase is to break down pullulan into smaller glucose molecules, which can then be further metabolized by microorganisms or utilized as a source of energy. This enzyme is commonly used in industries such as food processing and brewing to modify the properties of starch-based materials.