Abstract
We have previously reported that long chain acyl-CoA thioesterase activity was induced about 10-fold in rat liver mitochondria, when treating rats with the peroxisome proliferator di(2-ethylhexyl)phthalate (Wilcke M., and Alexson S. E. H (1994) Eur. J. Biochem. 222, 803-811). Here we have characterized two enzymes which are responsible for the majority of long chain acyl-CoA thioesterase activity in mitochondria from animals treated with peroxisome proliferators. A 40-kDa enzyme was purified and characterized as a very long chain acyl-CoA thioesterase (MTE-I). The second enzyme was partially purified and characterized as a long chain acyl-CoA thioesterase (MTE-II). MTE-I was inhibited by p-chloromercuribenzoic acid, which implicates the importance of a cysteine residue in, or close, to the active site. Antibodies against MTE-I demonstrated the presence of immunologically related acyl-CoA thioesterases in peroxisomes and cytosol. High expression of MTE-I was found in liver from peroxisome proliferator treated rats and in heart and brown fat from control and induced rats. Comparison of physical and catalytical characteristics of the enzymes studied here and previously purified acyl-CoA thioesterases suggest that MTE-I and MTE-II are novel enzymes.
Highlights
From the Wepartment of Metabolic Research, The Wenner-Gren Institute Arrhenius Laboratories F3, Stockholm University, S-106 91 Stockholm and the §Department of Medical Laboratory Sciences and Technology, Karolinska lnstitutet, Huddinge University Hospital, S-141 86 Huddinge, Sweden and the IIBiocenter Oulu, Department of Medical Biochemistry, University of Oulu, FIN-90 220 Oulu and the Department of Biochemistry and Biotechnology, University of Kuopio, P. 0
Several reports in the literature have indicated that rat liver mitochondria contain long chain acyl-CoA thioesterase activity that is regulated by peroxisome proliferators [8,9,10,11]
Induction of Acyl-GoA Thioesterase Activity in Percoll-purified Mitochondrial Fractions-Liver mitochondria from peroxisome proliferator-treated rats contained elevated long chain acyl-CoA thioesterase activity compared to mitochondria from control rats [10, 11], and as confirmed in this study
Summary
We have previously reported that long chain acyl-CoA thioesterase activity was induced about 10-fold in rat liver mitochondria, when treating rats with the peroxi· some proliferator di(2-ehtylhexyl)phtalate The second enzyme was par· tially purified and characterized as a long chain acyl· CoA thioesterase (MTE-11). Several reports in the literature have indicated that rat liver mitochondria contain long chain acyl-CoA thioesterase activity that is regulated by peroxisome proliferators [8,9,10,11]. Our results show that rat liver mitochondria contain several isoforms of long chain acyl-CoA thioesterase and in the present report two novel enzymes were characterized. It is tempting to speculate that acyl-CoA thioesterases may be potential regulators of fatty acid energy metabolism, a thioesterase capable of hydrolyzing palmitoyl-
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