Penicillin-binding protein 2B

Penicillin-binding protein 2B (PBP2B) is an essential bacterial enzyme responsible for forming peptide cross-links during cell wall assembly in Gram-positive bacteria, particularly *Streptococcus pneumoniae*. It functions as a monofunctional transpeptidase, crucial for peptidoglycan biosynthesis, cell division, and maintaining cell shape. PBP2B is a target for β-lactam antibiotics, but resistance can arise through amino acid substitutions that reduce antibiotic affinity while retaining sufficient enzymatic function.

β-lactam antibiotics covalently bind to the active-site serine residue within the transpeptidase domain, blocking cross-linking activity required for cell wall integrity.