Products of cholecystokinin (CCK)-octapeptide proteolysis interact with central CCK receptors.
Peptidases present in central nervous system (CNS) synaptic membranes, hydrolyze the neuroactive peptide cholecystokinin-octapeptide (CCK-8; Asp-Tyr-SO3H-Met-Gly-Trp-Met-Asp-Phe-NH2). In order to determine the pathway of degradation, synthetic CCK-8 was incubated at 37 degrees C with purified synaptic membranes; at various intervals reaction samples were removed from the reaction mixture and analysed by high-performance liquid chromatography to identify and quantify the peptide fragments. The results indicate an initial endopeptidase cleavage at the Met-Gly bond producing CCK-5 (Gly-Trp-Met-Asp-Phe-NH2). The carboxyl-terminal pentapeptide is further proteolysed to CCK-4 (Trp-Met-Asp-Phe-NH2) by a puromycin-sensitive aminopeptidase and to CCK-3 (Met-Asp-Phe-NH2) and Gly-Trp by an endopeptidase action. CCK-3 and CCK-2 appear to be relatively stable end-products. Moreover, these proteolytic fragments are shown to bind to the CCK receptor in brain with varying potencies.
Steardo
L
L
Knight
M
M
Tamminga
C A
CA
Chase
T N
TN
D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D010446:Peptide Fragments / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011949:Receptors, Cholecystokinin; D012844:Sincalide / Q000378:metabolism*; D013570:Synaptic Membranes / Q000378:metabolism
D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D011949:Receptors, Cholecystokinin; D010447:Peptide Hydrolases; D012844:Sincalide