Peptidoglykaner

Peptidoglykaner, also known as murein, are complex macromolecules that form the primary structural component of bacterial cell walls. They are essential for maintaining the shape and integrity of bacterial cells, protecting them from osmotic lysis. This intricate polymer consists of a repeating disaccharide backbone composed of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) units. These sugar chains are cross-linked by short peptide chains, which vary in composition depending on the bacterial species.

The synthesis of peptidoglycan is a complex process that occurs in several stages, beginning in the cytoplasm and culminating at the cell membrane. Enzymes called transpeptidases, also known as penicillin-binding proteins (PBPs), are crucial for forming the peptide cross-links. This cross-linking is what gives the cell wall its rigidity and strength.

The unique structure of peptidoglycan makes it a target for several antibiotics, most notably penicillin and its derivatives. These antibiotics inhibit the action of transpeptidases, preventing the proper formation of cross-links. Without a stable cell wall, bacteria, especially Gram-positive bacteria which have a thick peptidoglycan layer, are susceptible to bursting due to internal osmotic pressure. The absence of peptidoglycan in eukaryotic cells, including human cells, contributes to the selective toxicity of these antibiotics. Different bacterial types have varying amounts and arrangements of peptidoglycan, which is a basis for the Gram staining technique used in microbiology.