Characterization of in vitro proteolytic processing of beta-endorphin by reversed-phase HPLC.
In vitro, central and peripheral proteolytic processing of beta-endorphin by membrane-bound enzymes results in the formation of specific active fragments that have been recently shown to function in behavior, intestinal motility and in the central control of urinary bladder activity. A high resolution, reversed phase high performance liquid chromatography system capable of separating 28 beta-endorphin related fragments simultaneously was used to study the time-course processing of beta-endorphin by membrane associated peptidases in the brain and regions of the small intestine. The hypothesis we tested was that a homeostatic balance between alpha- and gamma-type endorphins exists in these tissues. The results of the study show that the rate and quantity of fragments produced between the mucosa and nerve-muscle regions of the small intestine are significantly different. Metabolic rates, pattern, and the ratio of alpha/gamma-type endorphins in the brain were very similar to the nerve-muscle region of the small intestine. This suggests that beta-endorphin processing to active fragments is occurring at the nerves of the small intestine and that a specific and similar balance of alpha/gamma-type endorphin exists in the brain and gastrointestinal system at neutral pH.
D000818:Animals; D001921:Brain / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004285:Dogs; D004723:Endorphins / Q000378:metabolism*; D005769:Gastrointestinal Motility; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D010477:Perfusion; D018822:alpha-Endorphin; D001615:beta-Endorphin; D018823:gamma-Endorphin
D004723:Endorphins; D010446:Peptide Fragments; D001615:beta-Endorphin; D018822:alpha-Endorphin; D018823:gamma-Endorphin; D010447:Peptide Hydrolases