The precursor protein is proteolytically cleaved to produce multiform beta-amylases and a 48 kDa alpha-amylase after secretion. Hydrolysis of (1->4)-alpha-D-glucosidic linkages in polysaccharides so as to remove successive maltose units from the non-reducing ends of the chains. 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. In the N-terminal section; belongs to the glycosyl hydrolase 14 family. In the C-terminal section; belongs to the glycosyl hydrolase 13 family.