Binding of vasoactive intestinal polypeptide to dispersed enterocytes results in rapid removal of the NH2-terminal histidyl residue.
Specific binding sites for 125I-labelled vasoactive intestinal polypeptide (VIP) (half-maximal inhibition at 1.5 +/- 0.2 nM VIP) were identified on dispersed porcine enterocytes. Radioactivity bound to the cell surface was internalized. At 37 degrees C, a steady state was achieved after 45 min with a ratio of internalized to cell surface-bound radioactivity of approximately 1:2 but at 10 degrees C, no radioactivity appeared intracellularly. Incubation of VIP with cells in the absence of inhibitors of proteolysis for as short a time as 30 s at 37 degrees C led to the formation of [des-His1]VIP by the action of amastatin- and bestatin-sensitive aminopeptidase(s). This metabolite was formed in the presence of sodium azide and when incubations were performed at 10 degrees C suggesting that internalization was not a prerequisite for degradation. As [des-His1]-VIP has only 1% of the bioactivity of VIP, formation of this metabolite will effectivily terminate the action of VIP in the epithelial layer of the intestine.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D004848:Epithelium / Q000378:metabolism; D006639:Histidine; D007583:Jejunum / Q000166:cytology / Q000378:metabolism*; D007700:Kinetics; D011964:Receptors, Gastrointestinal Hormone / Q000378:metabolism*; D018005:Receptors, Vasoactive Intestinal Peptide; D013552:Swine; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*
D000596:Amino Acids; D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide; D006639:Histidine