Beta-lactamase (Class A)

Class A beta-lactamases are enzymes produced by bacteria that confer resistance to beta-lactam antibiotics, such as penicillins and cephalosporins, by hydrolyzing the characteristic four-membered beta-lactam ring of these drugs. These enzymes are among the most clinically significant mechanisms of antibiotic resistance in Gram-negative bacteria. They are serine-based enzymes, utilizing an active site serine (Ser70) for catalysis. Key structural motifs include Ser70xxLys, SDN, KTG, and ExxLN. The hydrolysis reaction proceeds via a two-step acylation-deacylation mechanism. They primarily hydrolyze penicillins but many variants can also degrade cephalosporins. Their broad substrate range underlies much clinical resistance to multiple classes of antibiotics. Beta-lactamase inhibitors such as clavulanic acid target class A enzymes but some variants show reduced sensitivity due to mutations.

Hydrolyzes beta-lactam ring, inactivating the antibiotic.