title: Unique cleavage specificity of 'prohormone thiol protease' related to proenkephalin processing.
abstract: 'Prohormone thiol protease' (PTP) represents the major enkephalin precursor processing activity in chromaffin granules. In this study, cleavage specificity of PTP for paired basic and monobasic residues was examined with a series of model peptide-MCA (-methylcoumarinamide) substrates. Monobasic peptides were cleaved at the COOH- and NH2-terminal sides of the single basic residue. Dibasic peptides, however, were preferentially cleaved at the NH2-terminal side of the pair, or between the two basic residues, with low cleavage at the COOH-terminal side of the pair. Inhibition by the peptide inhibitor (D-Tyr)-Glu-Phe-Lys-Arg-CH2Cl provided further evidence for PTP's specificity for the dibasic Lys-Arg site. Inhibition by Z-Leu-Val-Gly-CHN2 and Z-Arg-Leu-Val-Gly-CHN2 suggests involvement of Val-Gly in substrate binding to PTP; these two cystatin C-related inhibitors also indicate PTP as a cysteine protease. These results demonstrate PTP's unique cleavage specificity that differs from other processing endopeptidases, including the subtilisin-related proprotein convertases, PC1/PC3, and PC2, as well as the pituitary proopiomelanocortin-converting enzyme, PCE. This study provides further evidence for PTP as a novel prohormone processing enzyme that belongs to the class of cysteine proteases.
authors.affiliation: Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, MD 20814.
authors.forename: A V
authors.initials: AV
authors.lastname: Azaryan
authors.forename: V Y
authors.initials: VY
authors.lastname: Hook
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D003374:Coumarins / Q000378:metabolism; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004745:Enkephalins / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D013379:Substrate Specificity
chemical_list: D003374:Coumarins; D015853:Cysteine Proteinase Inhibitors; D004745:Enkephalins; D011498:Protein Precursors; C029992:proenkephalin; D003546:Cysteine Endopeptidases; C083275:prohormone thiol protease