Peptidoglycan (PGN) (PGN)

Peptidoglycan, also known as murein, is an essential polymer that forms a mesh-like layer outside the plasma membrane of most bacteria, providing structural integrity and protection against osmotic lysis (StatPearls, 2023). It is composed of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) saccharide chains cross-linked by short amino acid pentapeptides (Wikipedia, 2024). This structure is a critical therapeutic target because it is unique to bacteria, allowing for high selective toxicity in antimicrobial therapy (NCBI, 2022). Major antibiotic classes, such as beta-lactams and glycopeptides, exert their bactericidal effects by inhibiting the synthesis or cross-linking of this layer (PubMed, 2021). Beyond its structural role, peptidoglycan serves as a potent signaling molecule for the host innate immune system, recognized by pattern recognition receptors like NOD1 and NOD2 to initiate an inflammatory response (Nature Reviews Microbiology, 2019). The integrity of the peptidoglycan layer is vital for bacterial survival, and its disruption leads to cell swelling and eventual lysis. Consequently, it remains one of the most successful targets in the history of drug development for treating bacterial infections.

Other names

MureinBacterial cell wallMucopeptideGlycopeptide polymer

Antibiotics targeting peptidoglycan typically inhibit its synthesis or assembly. Beta-lactams (e.g., penicillins, cephalosporins) bind to and inhibit penicillin-binding proteins (PBPs), which are enzymes that catalyze the transpeptidation step of cross-linking. Glycopeptides (e.g., vancomycin) bind to the D-alanyl-D-alanine terminus of the peptidoglycan precursor, sterically hindering the polymerization and cross-linking processes. Other agents like fosfomycin and cycloserine inhibit earlier cytoplasmic stages of peptidoglycan precursor synthesis (StatPearls, 2023; PubChem, 2024).