Probably a non-catalytic chitinase-like protein, which binds to insoluble chitin and enhances the activity of the catalytic chitinases (PubMed:16776685). Has weak chitin-binding activity (PubMed:27548813). Expressed in the peritrophic matrix of the midgut, and only very weakly in fecal pellets. Causes an allergic reaction in human (PubMed:16776685, PubMed:23075813, PubMed:27548813). Recombinant protein binds to IgE in 63% of the 27 patients tested allergic to house dust mite (HDM) (PubMed:16776685). The recombinant protein has 38%, 16% and 3% prevalences of IgE-binding with titers equal or above 0.1 ng/ml, 0.84 ng/ml and 10 ng/ml, respectively, of the 37 adult patients tested living in Perth, Australia allergic to European HDM (PubMed:23075813). Recombinant protein binds to IgE in 10% of the 91 adult Austrian patients tested allergic to European HDM. Binds to IgE in 15% of both the 20 and 13 patients tested with respiratory (asthma and allergic rhinitis) or skin (atopic dermatitis) manifestations, respectively. Induces activation of human basophils (PubMed:27548813). Belongs to the glycosyl hydrolase 18 family. Chitinase class II subfamily. Although it belongs to the glycosyl hydrolase 18 family, Ser-148 is present instead of the conserved Glu which is an active site residue. Therefore this protein may lack chitinase activity.