Chloramphenicol acetyltransferase

Chloramphenicol acetyltransferase (or CAT) is a bacterial enzyme that detoxifies the antibiotic chloramphenicol. It is responsible for chloramphenicol resistance in bacteria. This enzyme covalently attaches an acetyl group from acetyl-CoA to the chloramphenicol molecule so that it is unable to bind to the ribosome. CAT was used as a reporter system to measure the level of a promoter or its tissue-specific expression. The CAT assay involves monitoring acetylation of radioactive chloramphenicol on a TCA plate because acetylation significantly changes migration rate.