Important for breakdown of endosperm starch during germination. Endohydrolysis of (1->4)-alpha-D-glucosidic linkages in polysaccharides containing three or more (1->4)-alpha-linked D-glucose units. Binds 3 Ca(2+) ions per subunit. Monomer. In callus, weakly expressed. Expressed at a high level during germination in the aleurones cells under the control of the plant hormone gibberellic acid and in the developing grains at a low level. Belongs to the glycosyl hydrolase 13 family. Sequencing errors.