Unlikely to play an active role in the humoral immune defense. May have a function in the digestion of bacteria in the food. Hydrolysis of (1->4)-beta-linkages between N-acetylmuramic acid and N-acetyl-D-glucosamine residues in a peptidoglycan and between N-acetyl-D-glucosamine residues in chitodextrins. Found in the midgut, especially the epithelium of the gastric caeca. Expressed only during the larval stage, the highest level is reached during the third larval instar. Belongs to the glycosyl hydrolase 22 family.