#penicillinases

The 4-member ring of beta-lactam antibiotics gives these compounds a three-dimensional shape that mimics the D-Ala-D-Ala peptide terminus that serves as the natural substrate for transpeptidase activity during cell wall synthesis (Figure 1). As illustrated in Figure 2, tight binding of these drugs to the transpeptidase active site inhibits cell wall synthesis, resulting in a weakened cell wall that is susceptible to lysis during periods of cell growth. One of the major driving forces of cell lysis is the very high internal osmotic pressure present in bacteria, which is caused by the presence of a high concentration of proteins and other molecules that growing bacteria need to survive.