Inactivation of neurotensin by rat brain synaptic membranes. Cleavage at the Pro10-Tyr11 bond by endopeptidase 24.11 (enkephalinase) and a peptidase different from proline-endopeptidase.
It was shown previously that the tridecapeptide neurotensin is inactivated by rat brain synaptic membranes and that one of the primary inactivating cleavages occurs at the Pro10-Try11 peptide bond, leading to the formation of NT1-10 and NT11-13. The present study was designed to investigate the possibility that this cleavage was catalyzed by proline endopeptidase and/or endopeptidase 24.11 (enkephalinase). Purified rat brain synaptic membranes were found to contain a N-benzyloxycarbonyl-Gly-Pro-4-methyl-coumarinyl-7-amide-hydrolyzin g activity that was markedly inhibited (93%) by the proline endopeptidase inhibitor N-benzyloxycarbonyl-Pro-Prolinal and partially blocked (25%) by an antiproline endopeptidase antiserum. In contrast, the cleavage of neurotensin at the Pro10-Tyr11 bond by synaptic membranes was not affected by N-benzyloxycarbonyl-Pro-Prolinal and the antiserum. When the conversion of NT1-10 to NT1-8 by angiotensin converting enzyme was blocked by captopril and when the processing of NT11-13 by aminopeptidase(s) was inhibited by bestatin, it was found that thiorphan, a potent endopeptidase 24.11 inhibitor, partially decreased the formation of NT1-10 and NT11-13 by synaptic membranes.


CONCLUSIONS
(1) proline endopeptidase, although it is present in synaptic membranes, is not involved in the cleavage of neurotensin at the Pro10-Tyr11 bond; (2) endopeptidase 24.11 only partially contributes to this cleavage; (3) there exists in rat brain synaptic membranes a peptidase different from proline endopeptidase and endopeptidase 24.11 that is mainly responsible for inactivating neurotensin by cleaving at the Pro10-Tyr11 bond.
D000818:Animals; D002216:Captopril / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism*; D006868:Hydrolysis; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D015260:Neprilysin; D009496:Neurotensin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D011392:Proline / Q000378:metabolism; D000085822:Prolyl Oligopeptidases; D051381:Rats; D012697:Serine Endopeptidases; D013570:Synaptic Membranes / Q000187:drug effects / Q000201:enzymology*; D015244:Thiorphan; D008625:Tiopronin / Q000031:analogs & derivatives / Q000494:pharmacology; D014443:Tyrosine / Q000378:metabolism
D004151:Dipeptides; D010446:Peptide Fragments; D009496:Neurotensin; D014443:Tyrosine; C038541:N-benzyloxycarbonylprolylprolinal; D011392:Proline; D002216:Captopril; D015244:Thiorphan; D008625:Tiopronin; D010450:Endopeptidases; D010447:Peptide Hydrolases; D012697:Serine Endopeptidases; D000085822:Prolyl Oligopeptidases; D015260:Neprilysin; D007930:Leucine; C012211:ubenimex