Peptidoglycan-recognition protein that plays a key role in innate immunity by binding to murein peptidoglycans (PGN) of Gram-negative bacteria and activating the imd/Relish pathway. Has no activity against on Gram-positive bacteria. Binds to diaminopimelic acid-type PGN (DAP-type PGN), an activator of the imd/Relish pathway. Functions synergistically with PGRP-LC in producing resistance to E.coli and B.megaterium infections, which have the DAP-type peptidoglycan. Acts both upstream and in parallel with PGRP-LC in the imd/Relish pathway, and is required for infection-dependent activation of melanization. Required for Relish processing and nuclear translocation following proteolytic cleavage. Its localization suggests a role in the recognition and subsequent activation of the signaling at the first point of contact with invading bacteria. Monomer. Peptidoglycan binding induces oligomerization. However, no signal sequence are predicted by sequence analysis tools. Expressed in hemolymph. Localizes at the lumenal surface of the trachea (at protein level). Highly expressed in 0-5 hours embryos and in adult females, suggesting that it is expressed maternally. Belongs to the N-acetylmuramoyl-L-alanine amidase 2 family.