title: Liberation of enkephalins from enkephalin-containing peptides by brain endo-oligopeptidase A.
abstract: Endo-oligopeptidase A, highly purified from the cytosol fraction of bovine brain by immunoaffinity chromatography, has been characterised as a thiol endopeptidase. This enzyme, known to hydrolyse the Phe5-Ser6 bond of bradykinin and the Arg8-Arg9 bond of neurotensin has been shown to produce, by a single cleavage, [Leu]enkephalin or [Met]enkephalin from small enkephalin-containing peptides. Enkephalin formation could be inhibited in a concentration dependent manner by the alternative substrate bradykinin. The optimal substrate size was found to be 8-13 amino acids, with enkephalin the only product released from precursors in which this sequence is immediately followed by a pair of basic residues. However, the specificity constants (kcat/Km) obtained for endo-oligopeptidase A hydrolysis of bradykinin, neurotensin and dynorphin B are of the same order. Taken together, these results indicate that the substrate amino acid sequence is not the only factor determining the cleavage site of this enzyme. Finally, endo-oligopeptidase A and metalloendopeptidase EC 3.4.24.15 are two different enzymes. The latter is not able to liberate enkephalins from metorphamide and dynorphin.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology*; D002417:Cattle; D002846:Chromatography, Affinity; D003546:Cysteine Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004745:Enkephalins / Q000096:biosynthesis / Q000235:genetics*; D007106:Immune Sera; D007700:Kinetics; D008666:Metalloendopeptidases; D011499:Protein Processing, Post-Translational; D013379:Substrate Specificity
chemical_list: D004745:Enkephalins; D007106:Immune Sera; D003546:Cysteine Endopeptidases; D008666:Metalloendopeptidases; C022510:thimet oligopeptidase