Molecular cloning and expression of palmitoyl-protein thioesterase 2 (PPT2), a homolog of lysosomal palmitoyl-protein thioesterase with a distinct substrate specificity.
Palmitoyl-protein thioesterase is a lysosomal hydrolase that removes long chain fatty acyl groups from modified cysteine residues in proteins. Mutations in this enzyme were recently shown to underlie the hereditary neurodegenerative disorder, infantile neuronal ceroid lipofuscinosis, and lipid thioesters derived from acylated proteins were found to accumulate in lymphoblasts from individuals with the disorder. In the current study, we describe the cloning and expression of a second lysosomal thioesterase, palmitoyl-protein thioesterase 2 (PPT2), that shares an 18% identity with palmitoyl-protein thioesterase. Transient expression of a PPT2 cDNA led to the production of a glycosylated lysosomal protein with palmitoyl-CoA hydrolase activity comparable with palmitoyl-protein thioesterase. However, PPT2 did not remove palmitate groups from palmitoylated proteins that are substrates for palmitoyl-protein thioesterase. In cross-correction experiments, PPT2 did not abolish the accumulation of protein-derived lipid thioesters in palmitoyl-protein thioesterase-deficient cell lines. These results indicate that PPT2 is a lysosomal thioesterase that possesses a substrate specificity that is distinct from that of palmitoyl-protein thioesterase.
Soyombo
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AA
Department of Internal Medicine and the Hamon Center for Therapeutic Oncology Research, University of Texas Southwestern Medical Center, Dallas, Texas 75235-8593, USA.
Hofmann
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SL
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D019976:Cloning, Organism; D017124:Conserved Sequence; D018076:DNA, Complementary; D015723:Gene Library; D006801:Humans; D007527:Isoenzymes / Q000096:biosynthesis / Q000378:metabolism; D007700:Kinetics; D008168:Lung / Q000201:enzymology; D008247:Lysosomes / Q000201:enzymology; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D018076:DNA, Complementary; D007527:Isoenzymes; D011994:Recombinant Proteins; D013869:Thiolester Hydrolases; C095299:palmitoyl-protein thioesterase