Chloramphenicol acetyltransferase III (CAT III) (CAT III)

Chloramphenicol acetyltransferase III (CAT III) is a bacterial enzyme that provides resistance to the antibiotic chloramphenicol by inactivating it through covalent modification. The enzyme catalyzes the transfer of an acetyl group from acetyl-CoA to the 3-hydroxyl group of chloramphenicol, preventing the drug from binding to its target site on the 50S ribosomal subunit (UniProt: P00486). CAT III typically exists as a homotrimeric protein, where the active sites are located at the interfaces between adjacent subunits (PubMed: 2474411). This enzyme is frequently encoded on mobile genetic elements such as plasmids and transposons, which facilitates its rapid spread among pathogenic bacterial populations (PubMed: 1639244). While chloramphenicol is the primary substrate, CAT III is a significant focus for researchers developing inhibitors to combat antibiotic resistance. Its presence in clinical isolates is a major determinant of treatment failure for infections where chloramphenicol might otherwise be indicated.

Other names

Type III chloramphenicol acetyltransferaseCAT-IIIChloramphenicol 3-O-acetyltransferase

Catalyzes the O-acetylation of chloramphenicol at the C3 position using acetyl-CoA, which sterically hinders the antibiotic from binding to the bacterial 50S ribosomal subunit.