Peptidoglycan

Peptidoglycan (also called murein) is a unique and essential component of bacterial cell walls that provides structural integrity and protection. It is a heteropolymer composed of alternating amino sugar units, N-acetylglucosamine (GlcNAc) and N-acetylmuramic acid (MurNAc), forming a carbohydrate backbone. Each MurNAc unit is attached to a short peptide chain (typically 4-5 amino acids) containing L- and D-amino acids. The specific peptide composition varies between bacterial species; for example, Gram-negative bacteria often have L-alanine, D-glutamic acid, meso-diaminopimelic acid, and D-alanine, while Gram-positive bacteria frequently contain L-alanine, D-glutamine, L-lysine, and D-alanine, often with an interbridge. These peptide chains cross-link the glycan strands, creating a strong, mesh-like lattice structure. The thickness of the peptidoglycan layer differs significantly between bacterial types: Gram-positive bacteria have a thick layer (up to 40 layers, ~20% of cell wall dry weight), whereas Gram-negative bacteria have a much thinner layer (~10% of cell wall dry weight) located between the inner and outer membranes. Peptidoglycan is absent in human cells, making its biosynthesis a prime target for antibiotics.

Other names

murein

Inhibition of biosynthesis or degradation, leading to bacterial cell lysis. Antibiotics like penicillins inhibit the cross-linking of peptidoglycan chains.