Ambler class A beta-lactamase enzyme (class A β-lactamase)

Ambler class A beta-lactamase enzymes are a group of serine hydrolase enzymes produced by both Gram-negative and some Gram-positive bacteria that confer resistance to beta-lactam antibiotics, including penicillins, most cephalosporins, and monobactams, by hydrolyzing their characteristic four-membered beta-lactam ring[3][4][5]. Class A beta-lactamases are categorized based on their conserved sequence motifs, structure, and mechanistic features, notably utilizing a catalytic serine residue in the active site[1][5]. Prominent representatives in clinical resistance include TEM, SHV, CTX-M, and KPC subclasses, which are responsible for extended-spectrum beta-lactamase (ESBL) activity and, in some cases, resistance to carbapenems[1][4][5]. These enzymes are a major therapeutic target for beta-lactamase inhibitors in combination antibiotic strategies. The presence of class A beta-lactamases in bacterial pathogens is a key factor in the global crisis of antimicrobial resistance[4][5].

Other names

Class A beta-lactamaseClass A β-lactamaseSerine beta-lactamase class ATEM beta-lactamase (subfamily)SHV beta-lactamase (subfamily)CTX-M beta-lactamase (subfamily)KPC beta-lactamase (subfamily)

Hydrolyzes the beta-lactam ring of antibiotics, rendering them inactive[3][4]; Some inhibitors form a covalent bond with the catalytic serine to block activity[4]