| A cell wall polymer found in bacteria. It is a peptide cross-linked polysaccharide that forms a rigid structural scaffold around the cell.
The repeating saccharide unit is N-acetylglucosamine (NAG) / N-acetylmuramic acid (NAM), linked beta(1 -> 4).
CH2OH CH2OH
| |
C---O H C----O
/ \ |\ | / \
-C OH C | O | C C-
\ / / H \ \ /\ /
C---C C--\-C
| | | | \
H NHAc H | NHAc
|
O-CH(CH3)-C(=O)-N-PEPTIDE
This is cross-linked by short peptides, which have the unusual property of possesing D-amino acids. This tends to render the polymer resistant to proteases. Penicillin is a suicide inhibitor for the enzymes that cross-link the strands. Also lysozyme can cut the beta(1->4) links of the (NAG-NAM). Both of these cause the cell to lyse as the peptidoglycan breaks down. | 
