Acyl-CoA hydrolase enzyme, molecular model. This is an acyl-CoA thioesterase enzyme. Thioesterases hydrolyze coenzyme A (CoA) esters, producing the free acid and CoA. Thioesterases are a type of esterase, themselves a type of hydrolase, an enzyme that catalyses hydrolysis. The structure of this enzyme is hexameric, with six protein chains (colours). This example is from the bacterium Bacillus halodurans.