Alpha-amylase inhibitor, active against Z.subfasciatus alpha-amylase (ZSA) but not porcine pancreatic alpha-amylase (PPA). Has chitinase activity. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Homodimer. Belongs to the glycosyl hydrolase 18 family. Chitinase class II subfamily.