β-Lactam antibiotics contain a β-Lactam ring in their structure. They inhibit the synthesis of bacterial cell walls by interfering with transpeptidase, an enzyme involved in cross-linking peptidoglycan chains in the cell wall. Common examples of β-Lactam antibiotics are penicillin and cephalosporin. Penicillin inhibits transpeptidase, called penicillin binding proteins, preventing cross-linkage and stability of the bacterial cell wall.

1. β-Lactam Antibiotics
Dr. Somdutt Mujwar
(Associate Professor)
M.M. College of Pharmacy,
Maharishi Markandeshwar (Deemed to be University)
Mullana, Ambala- Haryana, India
Mobile: +91-9827813303

2. β-Lactam Antibiotics
 β-Lactams are the class of antibiotic drugs which are having β-Lactam
ring in their chemical structure.
 β-Lactam antibiotics inhibit the synthesis of bacteria cell wall.
 Examples of β-Lactam antibiotics are penicillin and cephalosporin.

3. β-Lactam Antibiotics
In case of Penicillin the β-Lactam ring is fused to thiazolidine ring while in the case of
Cephalosporin, it is fused to dihydrothizine ring

4. Mechanism of Action
 β-Lactam antibiotics interfere with the synthesis of bacterial cell wall.
 The bacteria synthesize UDP-N-acetylmuramic acid (NAM) and UDP-N-
acetylglucosamine (NAG), which links together forming long strands and
UDP is split off.
 The final step is separation of terminal D-alanine by the enzyme
transpeptidase for the formation o cross linkage between the neighboring
chains.

5.  Penicillin inhibits the transpeptidase so that cross linkage doesn’t takes
place and therefore no stability or rigidity was maintained in the bacterial
cell wall.
 Transpeptidase and related proteins are known as Penicillin binding
Proteins (PBP) and are present in every bacterial cell wall.

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