Overview
Peptidoglycan (murein) is the polymer of N-acetylglucosamine and N-acetylmuramic acid cross-linked by short peptides that forms the bacterial cell wall. It is a major pathogen-associated molecular pattern (PAMP) recognized by host TLR2 (intact peptidoglycan), NOD1 (meso-DAP fragments, Gram-negative), and NOD2 (muramyl dipeptide, both). Peptidoglycan recognition is central to innate immunity and to Crohn's disease (NOD2 mutations) haag 2015 intestinal microbiota innate immunity crohns.
Metal Connection
- Peptidoglycan recognition proteins (PGRPs) kill bacteria via three metal-dependent mechanisms: oxidative stress, thiol stress, and osmotic stress. PGRPs activate metal-mediated antimicrobial pathways — a direct intersection of innate immunity and metal toxicity kashyap 2014 pgrps kill bacteria metal stress.
- TLR2 signaling: Peptidoglycan-TLR2 activation in the esophagus drives IL-6 and il 8 production chen 2024 esophageal dysbiosis tlr2 barrier integrity gerd.
Cross-References
- innate immunity — peptidoglycan as PAMP
- toll like receptors — TLR2 recognizes peptidoglycan
- crohns disease — NOD2 mutations impair peptidoglycan sensing
- lipopolysaccharide — complementary Gram-negative PAMP (TLR4)