Table 1.
Overview of peptidoglycan recognition proteins in mammals and invertebrates
| Peptidoglycan recognition protein | Peptidoglycan fragment detected | Main effect | Main tissue distribution | Cellular localisation |
|---|---|---|---|---|
| MAMMALS (H. sapiens) | ||||
| PGLYRP 2 | GlcNAc‐MurNAc‐tetrapeptide | Amidase activity | Liver, skin, oral, intestinal | Soluble |
| PGLYRP 1,3,4 | GlcNAc‐MurNAc‐tetrapeptide | Bactericidal | PMN granules, skin, sweat glands, sebaceous glands, mouth, intestinal tract, eyes | Soluble (PGLYRP 3,4), PMN granules (PGLYRP 1) |
| Nod1 | Tripeptide: L‐Ala‐D‐Glu‐DAP | Activation of pro‐inflammatory pathway via NF‐κB signalling | Ubiquitous | Cytoplasm |
| Nod2 | GlcNAc‐MurNAc‐Ala‐Glu | Activation of pro‐inflammatory pathway via NF‐κB signalling | Monocytes | Cytoplasm |
| Lysozyme | MurNAc‐GlcNAc glycosidic bond | Muramidase activity; bactericidal effects | Phagocytic granules, serum, body secretions | Soluble |
| C‐type lectins (e.g. MBL, RegIII) | Glycan polymer | Complement activation; bactericidal effects | Serum | Soluble |
| INVERTEBRATES (D. melanogaster) | ||||
| PGRP‐L (multiple) | GlcNAc‐MurNAc‐tetrapeptide (Lys‐type) | Amidase activity; induction of antimicrobial peptides via activation of Imd pathway; phagocytosis | Haemocytes, fat body, gut, trachea, haemolymph | Cell surface, cytoplasm and soluble |
| PGRP‐S (multiple) | GlcNAc‐MurNAc‐tetrapeptide (DAP‐type) | Amidase activity; induction of antimicrobial peptides via activation of Toll pathway; phagocytosis; general bactericidal activity | Haemocytes, fat body, gut, trachea, epidermis, haemolymph | Soluble |
| Lysozyme | MurNAc‐GlcNAc glycosidic bond | Muramidase activity; general bactericidal activity | Gut, salivary glands | Soluble |
| C‐type lectins | Glycan polymer | Encapsulation; melanisation; bactericidal activity | Haemolymph, fat body | Cell surface and soluble |