Defense against chitin-containing fungal and bacterial pathogens. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. By glucan elicitor, and to a lesser extent by yeast extract, P.megasperma elicitor, UV light and dilution. Belongs to the glycosyl hydrolase 19 family. Chitinase class I subfamily.