Chloramphenicol Acetyltransferase, Escherichia coli, is a bacterial enzyme that detoxifies the antibiotic chloramphenicol, resulting in bacterial resistance to this antibiotic. This enzyme transfers an acetyl group from acetyl Coenzyme A to the chloramphenicol molecule, which prevents the antibiotic from binding to ribosomes. A histidine residue at the C-terminus of the enzyme plays a central role in its catalytic mechanism.