An aluminum silicate binding assay for quantitationof degradation of cholecystokinin octapeptide and other short peptides

Roman M. Janas, David L. Marks, Nicholas F. LaRusso

Research output: Contribution to journalArticle

5 Scopus citations


Most available techniques for the quantitation of enzymatic degradation of peptide hormones are time-consuming and require expensive equipment and/or novel reagents. Our aim here was to develop a rapid and sensitive assay for the measurement of degradation of cholecystokinin octapeptide (CCK-8) as well as other short, hydrophobic peptides. The proposed technique is based on our novel observation that intact CCK-8, but not its degradation product(s), binds to Lloyd reagent, a form of aluminum silicate. When radiolabeled CCK-8 was exposed to rat liver cytosol containing endogenous CCK-degrading activity, there was a time-dependent decrease in the binding of radiolabel to aluminum silicate [from 86 to 8% over 60 min at 37°C]. The decrease in binding closely paralleled the extent of CCK-8 degradation over time as assessed by high-performance liquid chromatography and immunoprecipitation with specific polyclonal antibodies to CCK-8. While aluminum silicate did not efficiently bind to C-terminal and N-terminal CCK tetrapeptides, magnesium silicate bound to both tetrapeptides (>82%), but not to their radiolabeled degradation products. Both aluminum and magnesium silicate also extensively bound (>82%) to other peptide hormones including Met-enkephalin, somatostatin, and secretin, but did not bind their degradation products. These binding assays will be useful in studies of peptidases which degrade cholecystokinin or other small, hydrophobic peptides.

Original languageEnglish (US)
Pages (from-to)6-11
Number of pages6
JournalAnalytical Biochemistry
Issue number1
StatePublished - Oct 1992


ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

Cite this