title: Opioid and other peptides as inhibitors of leumorphin (dynorphin B-29) converting activity.
abstract: A thiolprotease from rat brain membranes was shown to convert synthetic dynorphin B-29 (Dyn B-29, "leumorphin") to the tridecapeptide dynorphin B (Dyn B, "rimorphin"). This represents a "single-arginine cleavage" between threonine-13 and arginine-14 of the substrate. The dynorphin converting activity displayed typical Michaelis-Menten kinetics with an apparent Km for the substrate of 0.58 microM. Surprisingly, a synthetic peptide, Dyn B-29-(9-22), which contains the cleavage site, did not inhibit the activity. Dyn A inhibited the activity competitively with an apparent Ki of 3.7 microM. The converting activity was also inhibited by Dyn A-(6-17) but not by Dyn A-(8-17), suggesting a role of Arg6-Arg7 in the inhibition of converting activity. Bovine adrenal medulla Peptide E inhibited the converting activity substantially whereas metorphamide did not, suggesting the importance of COOH-terminal residues in recognition. Beta-Endorphin was an effective inhibitor of converting activity, and [alpha-N-acetyl]beta-endorphin was not, indicating a crucial role of the free NH2-terminus in recognition by the enzyme. ACTH inhibited the activity competitively with an apparent Ki of 39 nM. The converting activity was also inhibited substantially by ACTH-(1-13) but not by alpha-MSH, again indicating a requirement of the free NH2-terminus for recognition. The above results suggest that the converting enzyme recognizes peptides of the three known opioid gene families.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000201:enzymology*; D003546:Cysteine Endopeptidases; D010450:Endopeptidases / Q000302:isolation & purification; D004723:Endorphins / Q000494:pharmacology*; D004745:Enkephalins / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000201:enzymology; D011480:Protease Inhibitors; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D004723:Endorphins; D004745:Enkephalins; D011480:Protease Inhibitors; D011498:Protein Precursors; D000324:Adrenocorticotropic Hormone; C033660:preproenkephalin; D010450:Endopeptidases; D003546:Cysteine Endopeptidases