Peptidoglycan recognition protein 1, also known as Peptidoglycan recognition protein short, PGRP-S, PGLYRP1, PGLYRP, PGRP and TNFSF3L, is a secreted protein that belongs to the N-acetylmuramoyl-L-alanine amidase 2 family. PGLYRP1 / PGLYRP is highly expressed in bone marrow. It is weakly expressed in kidney, liver, small intestine, spleen, thymus, peripheral leukocyte, lung, fetal spleen and neutrophils. PGLYRP1 / PGLYRP is a pattern receptor that binds to murein peptidoglycans (PGN) of Gram-positive bacteria. It has bactericidal activity towards Gram-positive bacteria. PGLYRP1 / PGLYRP may kill Gram-positive bacteria by interfering with peptidoglycan biosynthesis. It binds also to Gram-negative bacteria, and has bacteriostatic activity towards Gram-negative bacteria. Peptidoglycan recognition proteins (PGRPs or PGLYRPs) are innate immunity proteins that are conserved from insects to mammals, recognize bacterial peptidoglycan, and function in antibacterial immunity and inflammation. Mammals have four PGRPs: PGLYRP1, PGLYRP2, PGLYRP3, and PGLYRP4. They are secreted proteins expressed in polymorphonuclear leukocytes (PGLYRP1), liver (PGLYRP2), or on body surfaces, mucous membranes, and in secretions (saliva, sweat) (PGLYRP3 and PGLYRP4). All PGRPs recognize bacterial peptidoglycan. The PGRPs likely play a role both in antibacterial defenses and several inflammatory diseases. They modulate local inflammatory responses in tissues (such as arthritic joints) and there is evidence for association of PGRPs with inflammatory diseases, such as psoriasis.