Class C β-Lactamases

Class C β-lactamases or AmpC enzymes are an important group of proteins that are broadly disseminated; they are encoded in the chromosomes of most Gram-negative rods, being constitutively or inducibly expressed although they may also be found as stable derepressions. Recently they have also been increasingly encountered as plasmid-mediated enzymes, therefore complicating the treatment of bacterial infections. It is also worth mentioning that these enzymes: (i) usually show a broad spectrum of β-lactam hydrolysis; (ii) may be overproduced in a bacterial cell (for the reasons cited above); (iii) are usually refractory to the action of classical β-lactamase inhibitors; and (iv) like other β-lactamases, can evolve by single amino acid mutations, thereby extending their substrate specificity. For all of these reasons, special attention must be paid to these β-lactamases in order to understand the specificity of their mechanism of action as well as their lack of response to the action of classical inhibitors. The search for pharmacological inhibitors of these enzymes must become a priority in future.