Molecular cloning of the peroxisome proliferator-induced 46-kDa cytosolic acyl-CoA thioesterase from mouse and rat liver--recombinant expression in Escherichia coli, tissue expression, and nutritional regulation.

Feeding clofibrate to rats and mice results in a strong induction of acyl-CoA thioesterase activity in the liver that is mainly due to increases in the enzyme activities in mitochondria and cytosol. The cytosolic acyl-CoA thioesterase protein of about 40 kDa, referred to as CTE-I, is strongly induced by the treatment. We report here the molecular cloning of the cDNA corresponding to the rat and mouse enzymes, and the further characterization of the mouse CTE-I by recombinant expression in bacteria and regulation of expression of the enzyme. The cDNAs corresponding to the rat and mouse enzymes contained open reading frames encoding proteins of 419 amino acids with calculated molecular masses of 45938 Da and 46135 Da, respectively. Sequence analysis revealed an active site serine consensus sequence commonly found in lipases and carboxylesterases. Recombinant expression of the mouse CTE-I cDNA in Escherichia coli resulted in production of immunoreactive protein that was mainly active with long-chain acyl-CoAs. Northern blot analysis showed that the full-length CTE-I cDNA probe hybridized to two major transcripts corresponding to CTE-I and MTE-I (mitochondrial acyl-CoA thioesterase I), respectively. The expression of both mRNA species was found to be highly regulated. As expected, both CTE-I and MTE-I were strongly upregulated (> 50-fold) by clofibrate treatment. Interestingly, fasting for 48 h resulted in a similar magnitude of induction as two days of clofibrate feeding. In addition, feeding a fat-free diet resulted in down-regulation of CTE-I mRNA. CTE-I mRNA was strongly expressed in kidney and brown adipose tissue and MTE-I mRNA was expressed mainly in brown adipose tissue and heart but was also expressed in kidney and white adipose tissue. Dietary regulation and tissue-specific expression suggest that CTE-I and MTE-I play important roles in lipid metabolism.