Aids in the digestion of starch and glycogen derived from food, such as skin scales, fungi and bacteria. 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. Inhibited by alpha-amylase inhibitors from wheat and rye. The most effective inhibitors are the wheat tetrameric alpha-amylase inhibitor (WTAI) and the rye dimeric alpha-amylase inhibitor (RDAI-1). Not inhibited by alpha-amylase inhibitor from barley. Optimum pH is 6.4. Monomer. Disulfide bonds are present. Causes an allergic reaction in human (PubMed:10545763, PubMed:1710630, PubMed:17845417). Binds to IgE in 30% of the 10 patients tested allergic to D.pteronyssinus, the European house dust mite (HDM) (PubMed:10545763). Binds to IgE in 46% of the 27 adults and in 25% of the 20 children tested allergic to mites (PubMed:1710630). The IgE of the mite-atopic tropical Australian Aboriginal patients binds unusually mainly to this protein, whereas this protein is a minor allergen in mite-atopic urban patients from Perth, including three patients of Aboriginal origin. IgE-binding to this protein is not the result of cross-reactivity to another amylase in these patients since IgE-binding to the extract from Culicoides, the biting midges common in the north west of Western Australia, is negative, as is the IgE-binding to the major allergen of B.tropicalis, a prevalent mite in the tropics. It is also unlikely that the IgE is induced by parasites, because parasitic infections also induce IgG4 antibody, which is mostly absent in the atopic Aboriginal population, although antibody to the Der p 4 allergen is occasionally detected. The amylases in mollusks could potentially be sensitizing, but mollusks are rarely consumed in the Aboriginal community (PubMed:17845417). The allergenicity of this protein is dependent on the presence of the disulfide bonds (PubMed:1710630). Common symptoms of mite allergy are bronchial asthma, allergic rhinitis and conjunctivitis (Probable). Belongs to the glycosyl hydrolase 13 family.