found in bacteria. It is a peptide
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).
C---O H C----O
/ \ |\ | / \
-C OH C | O | C C-
\ / / H \ \ /\ /
| | | | \
H NHAc H | NHAc
This is cross-linked by short peptides, which have the unusual property of possesing D-amino acid
s. 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.