Peptidoglycan

thumb|230px|Structure of peptidoglycan. Peptidoglycan (PG, murein) is the basic polymer of the bacterial wall.

It makes up 30 % of the G+ wall and 10 % of the G− bacteria (archea and mycoplasmas do no have it). Otherwise, it does not occur anywhere in nature.

Composition of peptidoglycan
Polymeric glycan chains of glucosamine and muramic acid (ie. glucosamine linked by ether bond to lactic acid) – diagnostic significance (only in bacteria). Glycan chains are linked by oligopeptide chains (they form a rigid network surounding the entire bacterium, thus maintaining its shape).

There are a number of variations (more than 100 structural types):
 * Type A;
 * Type B.

Ther presence of D-amino acids is a characteristic marker. Bound teichoic acids, polar and non-polar lipids.

Isolated PG shows biological activities:
 * pyrogenicity;
 * antigenicity;
 * complement activation.

Clinic
Inhibition of PG biosynthesis by β-lactam antibiotics, which bind to enzymes synthesizing PG interpeptide bridges, is important, causing bacterial cell lysis. Lysozyme acts as a bacteriolytic enzzyme (regulates bacterial colonizatio), cleaving the β-1,4 glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine.

related articles

 * Gram stain
 * Bacteria
 * Bacterial cell wall

Source

 * JULÁK, Jaroslav. Introduction to medical bacteriology. 1st edition. Prague: Karolinum, 2006.  ISBN 80-246-1270-4