The in vivo metabolism of cholecystokinin (CCK-8) is essentially ensured by aminopeptidase A.
The role of aminopeptidase A (APA) in inactivating cholecystokinin (CCK-8) was investigated in in vitro and in vivo experiments. EC 33 (3-amino-4-thio-butyl sulfonate), a selective APA inhibitor, decreased the formation of CCK7 after incubation of CCK-8 with rat brain synaptic membranes. The Km of purified APA for CCK-8, determined by quantifying CCK-7 production, was 144 microM and the Kcat 1400 s-1 . EC 33 protected endogenous CCK-like immunoreactivity (CCK-LI) released from brain slices by evoked depolarizations. The serine/thiol protease inhibitor Ala-Ala-Pro-Val-COCH2Cl (AAPV), alone or in combination with EC 33, did not modify significantly the level of CCK-LI released from the hippocampus, whereas it weakly protected the CCK-LI released from the cortex. Intracerebroventricular coadministration of CCK-8 and EC 33 in mouse brain led to a significant increase in the apparent affinity of CCK-8 as determined by the inhibition of the selective CCKB receptor agonist binding [3H]pBC 264 (ID50 = 88 pmol vs. 8250 pmol for CCK-8 alone); AAPV was less potent (ID50 = 445 pmol). In the same experiment the ID50 of pCCK-8, protected from aminopeptidases by a propionyl group was 86 pmol. These results strongly suggest that APA plays a major role in the inactivating pathway of CCK-8.
Migaud
M
M
Département de Pharmacochimie Moléculaire et Structurale, U266 INSERM-URA D1500 CNRS, Université René Descartes-Faculté de Pharmacie, Paris, France.
Durieux
C
C
Viereck
J
J
Soroca-Lucas
E
E
Fournié-Zaluski
M C
MC
Roques
B P
BP
D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism; D002552:Cerebral Ventricles / Q000187:drug effects / Q000502:physiology; D043384:Glutamyl Aminopeptidase; D006624:Hippocampus / Q000378:metabolism; D066298:In Vitro Techniques; D007276:Injections, Intraventricular; D007700:Kinetics; D008297:Male; D051379:Mice; D011480:Protease Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012844:Sincalide / Q000008:administration & dosage / Q000378:metabolism* / Q000494:pharmacology*; D013451:Sulfonic Acids / Q000494:pharmacology; D013570:Synaptic Membranes / Q000378:metabolism*
C101968:EC 33; D011480:Protease Inhibitors; D013451:Sulfonic Acids; D000626:Aminopeptidases; D043384:Glutamyl Aminopeptidase; D012844:Sincalide