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Evidence that CCK-58 has structure that influences its biological activity
J R Reeve1, V E Eysselein, G Rosenquist
1CURE Digestive Diseases Research Center, Department of Veterans Affairs, West Los Angeles 90073, USA.
The American Journal of Physiology
|May 11, 1996
Summary
Cholecystokinin-58 (CCK-58) has a unique structure that shields its active site, influencing its bioactivity. This shielding effect was demonstrated by comparing CCK-58
Area of Science:
- Peptide Biology
- Gastrointestinal Physiology
- Endocrinology
Background:
- Biologically active peptides often exist in multiple forms, but the functional roles of non-bioactive regions remain unclear.
- Cholecystokinin (CCK) is a key gastrointestinal hormone involved in digestion and satiety, with various molecular forms identified.
Purpose of the Study:
- To investigate the structural basis of cholecystokinin-58 (CCK-58) bioactivity.
- To determine if the amino terminus of CCK-58 influences its biological activity.
Main Methods:
- Purification of CCK-58 from canine intestinal mucosa using reverse-phase chromatography.
- Amino acid analysis to determine peptide concentrations of purified CCK-58 and synthetic CCK-8.
- Enzymatic assays comparing amylase release from pancreatic acini by CCK-58 and CCK-8 before and after tryptic digestion.
Main Results:
- Tryptic digestion of CCK-58 significantly reduced its EC50 for amylase release, from 96 pM to 28 pM, similar to CCK-8 (17 pM).
- Carboxyl fragments of CCK-58 generated by trypsin or acid hydrolysis were more immunoreactive than intact CCK-58.
- These findings suggest that the structure of CCK-58 shields its bioactive carboxyl terminus.
Conclusions:
- CCK-58 possesses a unique structure that influences its bioactivity by shielding the carboxyl terminus.
- This structural shielding impacts both the biological and immunological activities of CCK-58.
- The study highlights the functional significance of regions outside the core bioactive sequence in peptide hormones.