Serine beta-lactamase class C (AmpC (commonly used for the main representative enzyme))

Serine beta-lactamases of Ambler class C are enzymes produced by many Gram-negative bacteria that confer resistance to a broad range of β-lactam antibiotics, particularly cephalosporins. These enzymes act by hydrolyzing the β-lactam ring—a critical structure required for antibiotic activity—using an active site serine residue. The most well-known member is AmpC. Class C β‑lactamases are typically encoded on bacterial chromosomes but can also be found on plasmids, facilitating their spread between species. They play a major role in hospital-acquired infections caused by Enterobacterales and Pseudomonadales. Molecularly, they belong to the serine hydrolases and share conserved sequence motifs such as S64XXK at their active site[1][6]. Their action undermines many commonly used β‑lactams except carbapenems and fourth-generation cephalosporins unless further mutations occur. Some new non-beta‑lactone-based inhibitors can target these enzymes but traditional inhibitors like clavulanic acid are ineffective. The presence or upregulation of these enzymes is an important biomarker for predicting treatment failure with certain classes of antibiotics. Their rapid evolution poses significant challenges in antimicrobial therapy due to limited effective drugs remaining when they are present[1][2][5].

Other names

Class C beta-lactamaseCephalosporinaseAmpC beta-lactamaseAmbler class C beta-lactamase

Hydrolyzes the amide bond in the beta-lactam ring of susceptible antibiotics via a serine-based catalytic mechanism, rendering them inactive[1][2][3].