Structural highlights
Function[PPT1_BOVIN] Removes thioester-linked fatty acyl groups such as palmitate from modified cysteine residues in proteins or peptides during lysosomal degradation. Prefers acyl chain lengths of 14 to 18 carbons. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPalmitoyl-protein thioesterase-1 (PPT1) is a newly described lysosomal enzyme that hydrolyzes long chain fatty acids from lipid-modified cysteine residues in proteins. Deficiency in this enzyme results in a severe neurodegenerative storage disorder, infantile neuronal ceroid lipofuscinosis. Although the primary structure of PPT1 contains a serine lipase consensus sequence, the enzyme is insensitive to commonly used serine-modifying reagents phenylmethylsulfonyl fluoride (PMSF) and diisopropylfluorophosphate. In the current paper, we show that the active site serine in PPT1 is modified by a substrate analog of PMSF, hexadecylsulfonylfluoride (HDSF) in a specific and site-directed manner. The apparent K(i) of the inhibition was 125 micrometer (in the presence of 1.5 mm Triton X-100), and the catalytic rate constant for sulfonylation (k(2)) was 3.3/min, a value similar to previously described sulfonylation reactions. PPT1 was crystallized after inactivation with HDSF, and the structure of the inactive form was determined to 2.4 A resolution. The hexadecylsulfonyl was found to modify serine 115 and to snake through a narrow hydrophobic channel that would not accommodate an aromatic sulfonyl fluoride. Therefore, the geometry of the active site accounts for the reactivity of PPT1 with HDSF but not PMSF. These observations suggest a structural explanation as to why certain serine lipases are resistant to modification by commonly used serine-modifying reagents. Structural basis for the insensitivity of a serine enzyme (palmitoyl-protein thioesterase) to phenylmethylsulfonyl fluoride.,Das AK, Bellizzi JJ 3rd, Tandel S, Biehl E, Clardy J, Hofmann SL J Biol Chem. 2000 Aug 4;275(31):23847-51. PMID:10801859[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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