Endohydrolysis of (1->4)-alpha-D-glucosidic linkages in polysaccharides containing three or more (1->4)-alpha-linked D-glucose units. Binds 1 Ca(2+) ion per subunit. Binds 1 Cl(-) ion per subunit. Activated by chloride ions. Inhibited by acarbose. Not inhibited by wheat alpha-amylase inhibitors 1 (WI-1, the tetrameric form) or 3 (WI-3, the monomeric form) and bean alpha-amylase inhibitor 1 (alphaAI-1). Optimum pH is 6.5. Active in slightly acidic to neutral pH range. Monomer. Causes an allergic reaction in human. Binds to IgE of patients allergic to house dust mite. Belongs to the glycosyl hydrolase 13 family.