Fatty acid biosynthesis chain termination and release of the free fatty acid product is achieved by hydrolysis of the thio ester by a thioesterase. This thioesterase may be associated with peroxisome proliferation and may play a role in the production of 3-hydroxy fatty acid diester pheromones. Highest levels in uropygial gland, much lower in liver and kidney. Belongs to the type-B carboxylesterase/lipase family.