Acyl-coenzyme A thioesterase 8, also known as ACOT8, are a group of enzymes that catalyze the hydrolysis of acyl-CoAs to the free fatty acid and coenzyme A (CoASH), providing the potential to regulate intracellular levels of acyl-CoAs, free fatty acids and CoASH. This protein may mediate Nef-induced down-regulation of CD4. It competes with BAAT (Bile acid CoA: amino acid N-acyltransferase) for bile acid-CoA substrate (such as chenodeoxycholoyl-CoA). ACOT8 shows a preference for medium-length fatty acyl-CoAs. Recombinant human ACOT8 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.