N-terminal fragments of intestinal cholecystokinin: evidence for release of CCK-8 by cleavage on the carboxyl side of Arg74 of proCCK.
From porcine duodenal mucosa we have identified three major procholecystokinin (proCCK) fragments: desoctaCCK-33, desnonaCCK-33 and desnonaCCK-39. (DesoctaCCK-33 means CCK-33 devoid of the 8 C-terminal amino acids, etc.). The fragments were purified by immunoaffinity chromatography and three steps of reverse phase HPLC monitored by a radioimmunoassay specific for the N-terminal part of CCK-33. The structures could be deduced from the proCCK sequence by N-terminal sequence determination and mass spectrometry. Whereas desnona-fragments of CCK have been described before, this is the first finding of a desoctaCCK, and it indicates that CCK-8 is released from the longer forms by endogenous cleavage of the Arg-Asp-bond. A carboxypeptidase B-like exopeptidase subsequently must produce the desnona-fragments by removing the arginine residue.
Blanke
S E
SE
Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Denmark.
Johnsen
A H
AH
Rehfeld
J F
JF
D000595:Amino Acid Sequence; D000818:Animals; D002766:Cholecystokinin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002846:Chromatography, Affinity; D002851:Chromatography, High Pressure Liquid; D004386:Duodenum / Q000737:chemistry; D005629:Frozen Sections; D007413:Intestinal Mucosa / Q000737:chemistry*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D011498:Protein Precursors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D011863:Radioimmunoassay; D012844:Sincalide / Q000378:metabolism*; D013552:Swine
D011498:Protein Precursors; C060249:procholecystokinin; C032740:cholecystokinin 39; D002766:Cholecystokinin; D012844:Sincalide