What is the mechanism of action of penicillin?

Penicillin functions primarily by blocking the transpeptidase enzyme, which is crucial for the cross-linking of peptidoglycan layers in bacterial cell walls. This action disrupts the structural integrity of the cell wall, leading to cell lysis and death, particularly in actively dividing bacteria. The transpeptidation process is essential in forming rigid cell walls necessary for bacterial survival, and by inhibiting this process, penicillin effectively targets a critical aspect of bacterial physiology.

The penicillin molecule itself mimics the D-alanyl-D-alanine portion of the peptidoglycan precursors, which allows it to bind to the active site of transpeptidases, also known as penicillin-binding proteins (PBPs). This binding prevents the enzyme from performing its normal function, leading to a weakened cell wall and ultimately causing cell death, particularly in gram-positive bacteria that rely heavily on this structure for stability.

Understanding the mechanism of action of penicillin is crucial for appreciating its role in treating bacterial infections and the basis for bacterial resistance mechanisms, such as the production of beta-lactamases, which are enzymes that can inactivate penicillin and similar antibiotics. Other drug options mentioned do not relate directly to the action of penicillin