Binds specifically to peptidoglycan and triggers the propenoloxidase cascade which is an important insect defense mechanism. Monomer. Constitutively expressed in fat body, epithelial cells and hemocytes. Not detected in Malpighian tubules, silk gland or midgut. By bacterial challenge. Belongs to the N-acetylmuramoyl-L-alanine amidase 2 family.