Defense against chitin-containing fungal pathogens. Binds the hyphal tips, lateral walls and septa of fungi and degrades mature chitin. Random endo-hydrolysis of N-acetyl-beta-D-glucosaminide (1->4)-beta-linkages in chitin and chitodextrins. Optimum pH is about 5.0. Stable between pH 4-8. Enzyme activity is retained almost fully under 40 degrees Celsius and completely destroyed at 70 degrees Celsius. At 60 degrees Celsius the activity was over 80% compared to the untreated enzyme. Localized in the aleurone cells of the seed endosperm (at protein level). Levels increase from 23 to 40 days after flowering, and are maintained until maturation (at protein level). Belongs to the glycosyl hydrolase 19 family. Chitinase class I subfamily.