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. Salivary gland. Only expressed in adults. Belongs to the glycosyl hydrolase 22 family.