Peptidoglycan

Peptidoglycan (also known as murein) is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of most bacteria, forming the cell wall. The sugar component consists of alternating residues of beta-(1,4) linked N-acetylglucosamine and N-acetylmuramic acid. Attached to the N-acetylmuramic acid is a peptide chain of three to five amino acids. The peptide chain can be cross-linked to the peptide chain of another strand forming the 3D mesh-like layer.

Structure

Peptidoglycan serves a structural role in the bacterial cell wall, giving structural strength, as well as counteracting the osmotic pressure of the cytoplasm. Peptidoglycan is also involved in binary fission during bacterial cell reproduction.

Biosynthesis

The biosynthesis of peptidoglycan is a multi-step process that takes place in the cytoplasm and on the inner side of the bacterial cell membrane. The final stages of peptidoglycan synthesis involve the insertion of the peptidoglycan subunits onto the existing peptidoglycan.

Function

Peptidoglycan is a critical component of the bacterial cell wall, providing rigidity and maintaining the overall shape of the cell. It also provides a physical barrier against osmotic lysis, mechanical forces, and predatory organisms.

Clinical significance

Peptidoglycan is a major target for antibiotics such as penicillin, which inhibits its cross-linking. In humans, recognition of peptidoglycan is likely to be of importance in the innate immune response to infection.

See also

• Cell wall
• Gram-positive bacteria
• Gram-negative bacteria
• Antibiotics

References

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