Able to cleave chitin oligomers from N=3 to 6. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Homodimer, but homotrimers and homotetramers could be observed for the 20.5 and 30 kDa chitinases. The 70 kDa chitinase is probably the precursor protein of the 30 and 20.5 kDa chitinases. Belongs to the glycosyl hydrolase 18 family. Chitinase class II subfamily.