Cross-reactivity of a monoclonal anti-[Met5]enkephalin antibody with cholecystokinin peptides

Abstract

The hypothesis of a conformational similarity between the unsulfated form of cholecystokinin C-terminal heptapeptide and [Met⁵]enkephalin was proposed by Schiller and colleagues. To test this possibility, we investigated the competition of cholecystokinin C-terminal peptides for the binding to a monoclonal anti-[Met⁵]enkephalin antibody. We observed that the antibody immunoprecipitated cholecystokinin peptides having at least the six C-terminal amino acids. Unlike the opiate receptors which had no affinity for the sulfated heptapeptide, the monoclonal antibody recognized the sulfated form of the C-terminal octapeptide of cholecystokinin.