Thioesterases are enzymes that hydrolyse thioesters between a carbonyl group and a sulfur atom. in the presence of water, and are identified as members of E.C.3.1.2. Substrates of 15 of these 27 groupings contain coenzyme A (CoA), two contain acyl carrier proteins (ACPs), four have glutathione or its derivatives, one has ubiquitin, and two contain other moieties. Acetyl-CoA hydrolase, palmitoyl-CoA hydrolase, succinyl-CoA hydrolase, formyl-CoA hydrolase, acyl-CoA hydrolase are a few examples of this group of enzymes[1].