Evidence that cck-58 has structure that influences its biological
activity.
Reeve, Joseph R., Viktor E. Eysselein, Grace Rosenquist, Joerg Zeeh,
Ulrike Regner, F. J. Ho, Peter Chew, Michael T. Davis, Terry D. Lee,
John E. Shively, Scott R. Brazer, and Rodger A. Liddle.
CURE/VA/UCLA Gastroenteric Biology Center, VA Wadsworth, Los
Angeles, CA 90073, Division of Gastroenterology, Harbor/UCLA Medical
Center, Torrance, CA 90509, Department Animal Physiology, University
of California, Davis, CA 95616, Division of Gastroenterology,
University of Essen, 4300 Essen, Germany, Division of
Gastroenterology, Department of Medicine, University of Mannheim,
6800 Mannheim, Germany, Division of Immunology, Beckman Research
Institute of the City of Hope Research Institute, Duarte, CA 91010,
Department of Medicine, Duke University and Durham VA Medical
Centers, Durham NC 27710
APStracts 2:0257G, 1995.
Many biologically active peptides exist in multiple molecular forms,
but the functional significance of regions outside the region of
bioactivity is unknown. The biological and immunological data
presented in this paper indicate that cholecystokinin-58 (CCK-58),
unlike other forms of cholecystokinin has structure that influences
its bioactivity. CCK-58 was purified from acid extracts of canine
intestinal mucosa until a single absorbance peak was obtained during
reverse phase chromatography. Amino acid analysis precisely
determined the peptide concentrations of purified CCK-58 and
synthetic CCK-8. Our hypothesis was that if the amino terminus of
CCK-58 influences its bioactivity this would be modified when this
region was removed from the peptide. To evaluate the importance of
the amino terminus of CCK-58 to influence its biological activity,
the abilities of CCK-58 and CCK-8 to release amylase from pancreatic
acini were compared, before and after tryptic digestion. Tryptic
digestion of CCK-58 decreased the EC50 for amylase release from 96 pM
to 28 pM. The EC50 for digested CCK-58 was similar to that for CCK-8
(17 pM). These results suggest that CCK-58 has structure that shields
its bioactive carboxyl terminus. This is further supported by the
finding that carboxyl fragments generated from CCK-58 by trypsin or
by partial acid hydrolysis were more than two fold more
immunoreactive than the intact CCK-58. The diminished activity of
CCK-58 indicates that the amino terminus of CCK-58 shields the
carboxyl terminus which is important to its biological and
immunological activities.
Received 31 January 1994; accepted in final form 9 May 1995.
APS Manuscript Number G41-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 December 95