Transpeptidase Inhibitors

The bacterial D,D-transpeptidases, also called penicillin-binding proteins, catalyse the cross-linking of peptidoglycan that gives the cell wall its strength and the cell its rod shape. Drugs in this class inactivate those enzymes, so a growing bacterium builds an un-cross-linked wall and lyses under its own osmotic pressure - which is why they kill dividing organisms and spare resting ones. The class is the mechanistic name for the beta-lactams: FDA's ranking of antimicrobial importance lists the penicillins (natural, penicillinase-stable, carboxy-, ureido- and aminopenicillins) and the cephalosporins by generation, with the aminopenicillins and the later cephalosporins ranked critically important in human medicine.