Beta-lactamase (class A, class C, and class D variants)

Beta-lactamases are bacterial enzymes classified into molecular classes (A, C, and D) based on amino acid sequence and function; all use a serine residue at their active site to hydrolyze beta-lactam antibiotics, conferring resistance to penicillins, cephalosporins, carbapenems, and monobactams depending on type. Class A enzymes include common ESBLs (TEM, SHV, CTX-M, KPC), class C enzymes are largely cephalosporinases (AmpC-type), and class D includes diverse OXA-type enzymes. These enzymes represent a major mechanism of acquired and intrinsic antibiotic resistance among clinically significant bacteria; inhibitors such as clavulanic acid, tazobactam, and avibactam are used to restore antibiotic activity against some enzyme types, although resistance continues to evolve, presenting major challenges in infectious disease therapy and patient safety.

Other names

PenicillinaseCephalosporinase (class C)Serine beta-lactamaseESBLs (Extended-Spectrum Beta-Lactamases; for some class A/D)AmpC (class C)OXA-type beta-lactamase (for some class D)KPC, SHV, TEM, CTX-M (examples of class A beta-lactamases)

Beta-lactam antibiotics: bind and are hydrolyzed/inactivated unless the enzyme is inhibited or overcome. Beta-lactamase inhibitors: bind and inhibit the enzyme, restoring antibiotic efficacy.