Mammalian liver contains an activity which mimics bacterial chloramphenicol acetyltransferase.

Rat liver extracts contain an activity which mimics Escherichia coli chloramphenicol acetyltransferase (CAT); the latter is commonly used to report transcriptional activation of chimeric genes transfected into cultured cells. Although the activities are indistinguishable by the standard thin-layer chromatography assay, alternate methods can discriminate between them. The rat CAT-like activity appears to be an integral membrane protein. It was observed in the microsomal fraction of both liver and kidney. Similarly CAT-like activities were detected in mouse, rabbit and pig liver. In addition, liver homogenates which contain the CAT-like activity also contain a heat-labile inhibitor of (authentic) bacterial CAT.