title: Further characterization of an enkephalin-generating enzyme from adrenal medullary chromaffin granules.
abstract: An adrenomedullary protease capable of generating Met5-enkephalin from endogenous precursor(s) has been purified 1,000-fold using affinity chromatography in combination with gel filtration. This trypsin-like enzyme has an apparent molecular weight of 20,000 daltons by gel filtration. The reactivity of the enzyme toward several fluorogenic peptides, Peptides E and F, and the heptapeptides, Met5-enkephalin-Arg6-Phe7 and Met5-enkephalin-Arg6-Arg7, was examined. The two heptapeptides and the fluorogenic compounds were poor substrates for the adrenal enzyme; in contrast, Peptides E and F were cleaved. The low molecular weight products of Peptide F digestion were identified by HPLC as Arg1-Met6-enkephalin, Met5-enkephalin, and Met5-enkephalin-Lys6, while digestion of Peptide E resulted in the production of Leu5-enkephalin and Met5-enkephalin-Arg6-Arg7. [3H]-beta m-Lipotropin was not hydrolyzed by the adrenal enzyme. These results indicate that this adreno-medullary protease is capable of cleaving adrenal opioid peptides at the paired basic sites and thus represents a possible candidate for a proenkephalin-converting enzyme.
mesh_terms: D000313:Adrenal Medulla / Q000201:enzymology*; D000818:Animals; D002417:Cattle; D002837:Chromaffin Granules / Q000201:enzymology*; D002838:Chromaffin System / Q000201:enzymology*; D010450:Endopeptidases / Q000302:isolation & purification / Q000378:metabolism*; D004745:Enkephalins / Q000096:biosynthesis*; D007700:Kinetics; D008970:Molecular Weight; D011480:Protease Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D014357:Trypsin
chemical_list: D004745:Enkephalins; D011480:Protease Inhibitors; D010450:Endopeptidases; D014357:Trypsin; C027374:Met-enk forming enzyme