Molecular cloning and characterization of two mouse peroxisome proliferator-activated receptor alpha (PPARalpha)-regulated peroxisomal acyl-CoA thioesterases.
Peroxisomes are organelles that function in the beta-oxidation of long- and very long-chain acyl-CoAs, bile acid-CoA intermediates, prostaglandins, leukotrienes, thromboxanes, dicarboxylic fatty acids, pristanic acid, and xenobiotic carboxylic acids. The very long- and long-chain acyl-CoAs are mainly chain-shortened and then transported to mitochondria for further metabolism. We have now identified and characterized two peroxisomal acyl-CoA thioesterases, named PTE-Ia and PTE-Ic, that hydrolyze acyl-CoAs to the free fatty acid and coenzyme A. PTE-Ia and PTE-Ic show 82% sequence identity at the amino acid level, and a putative peroxisomal type 1 targeting signal of -AKL was identified at the carboxyl-terminal end of both proteins. Localization experiments using green fluorescent fusion protein showed PTE-Ia and PTE-Ic to be localized in peroxisomes. Despite their high level of sequence identity, we show that PTE-Ia is mainly active on long-chain acyl-CoAs, whereas PTE-Ic is mainly active on medium-chain acyl-CoAs. Lack of regulation of enzyme activity by free CoASH suggests that PTE-Ia and PTE-Ic regulate intraperoxisomal levels of acyl-CoA, and they may have a function in termination of beta-oxidation of fatty acids of different chain lengths. Tissue expression studies revealed that PTE-Ia is highly expressed in kidney, whereas PTE-Ic is most highly expressed in spleen, brain, testis, and proximal and distal intestine. Both PTE-Ia and PTE-Ic were highly up-regulated in mouse liver by treatment with the peroxisome proliferator WY-14,643 and by fasting in a peroxisome proliferator-activated receptor alpha-dependent manner. These data show that PTE-Ia and PTE-Ic have different functions based on different substrate specificities and tissue expression.
Westin
Maria A K
MA
Department of Laboratory Medicine, Karolinska Institutet, C1-74, Karolinska University Hospital at Huddinge, SE-141 86 Stockholm, Sweden.
Alexson
Stefan E H
SE
Hunt
Mary C
MC
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D003600:Cytosol / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D005786:Gene Expression Regulation; D049452:Green Fluorescent Proteins; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008099:Liver / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D020675:Peroxisomes / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011743:Pyrimidines / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D012867:Skin / Q000378:metabolism; D013869:Thiolester Hydrolases / Q000737:chemistry* / Q000378:metabolism; D013997:Time Factors; D014018:Tissue Distribution; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics*; D014162:Transfection; D015854:Up-Regulation
D018076:DNA, Complementary; D008164:Luminescent Proteins; D011743:Pyrimidines; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; D014157:Transcription Factors; D049452:Green Fluorescent Proteins; C006253:pirinixic acid; D013869:Thiolester Hydrolases; C447830:Acot1 protein, mouse; D010100:Oxygen