Calcium-binding enzyme that initiates starch digestion in the oral cavity (PubMed:12527308). Catalyzes the hydrolysis of internal (1->4)-alpha-D-glucosidic bonds, yielding a mixture of maltose, isomaltose, small amounts of glucose as well as small linear and branched oligosaccharides called dextrins (PubMed:12527308). 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. Monomer. Belongs to the glycosyl hydrolase 13 family. Three distinct genes (AMY1A, AMY1B and AMY1C), located in a gene cluster on 1p21, encode proteins sharing the same peptidic sequence. Amylase entry