Molecular cloning and sequencing of thioesterase B cDNA and stimulation of expression of the thioesterase B gene associated with hormonal induction of peroxisome proliferation

Abstract

The primary structure deduced from the cDNA of a medium-chain fatty acyl-CoA hydrolase designated thioesterase B from the uropygial gland of mallard duck was determined. A near full-length thioesterase B cDNA was isolated from a duck uropygial gland cDNA library using a 120-base pair polymerase chain reaction probe generated from first strand of cDNA and primers synthesized on the basis of two segments of the enzyme. The nucleotide sequence of this cDNA showed an open reading frame encoding a polypeptide of 557 amino acids including a 25-amino acid leader sequence. It showed little homology to the thioesterase domain of fatty acid synthase and S-acyl fatty acid synthase thioesterase, but showed homology to some esterases such as carboxylesterases. Northern blot showed one major transcript at 2.4 kilobases. The highest level of this transcript was in the uropygial gland, much less in the liver and kidney, and not detectable in other organs. Elevation of thioesterase B transcript level was associated with peroxisome proliferation occurring in the mating season and the increase in transcript level correlated with peroxisome proliferation and synthesis of 3-hydroxyfatty acid diester pheromones resulting from estradiol treatment. This thioesterase may be associated with peroxisome proliferation or peroxisomal metabolism.