AADAC is a 45 kDa membrane-associated hydrolase highly expressed in the human liver that has been implicated in the hydrolysis of arylacetamide xenobiotics including flutamide and phenacetin.556¨C560AADAC is highly homologous to several related lipases, AADACL1, 2, and 4, the latter two of which remain completely unannotated. Overexpression of AADAC in a rat hepatoma cell line produces changes in cellular TG levels, apoplipoprotein B secretion, and fatty acid oxidation, but the mechanism for these effects remains unclear.561?Candidate endogenous substrates, selective inhibitors, or knockout mice have not, to our knowledge, been described for AADAC or the related enzymes AADACL2 and AADACL4.