title: Subcellular distribution of proteolytic activities degrading bioactive peptides and analogues in the rat small intestinal and colonic enterocytes.
abstract: The objective of this study was to compare, in rat small intestinal and colonic enterocytes, subcellular distributions of activities degrading the large peptides, neurotensin, acetylneurotensin (8-13), GRF(1-29)NH2 (human growth hormone releasing factor fragment), (desNH2Tyr1,D-Ala2,Ala15)-GRF(1-29)NH2, insulin, and insulin B-chain. Proteolytic activities degrading individual peptides in the 10,000-g pellet, rich in intracellular organelles, 27,000-g pellet, rich in brush-border membrane, 100,000-g pellet, and 100,000-g supernatant, rich in cytosol, were determined and compared for both the small intestine and colon. In colonic fractions, the cytosol had highest activity (g protein)-1 degrading three out of four peptides tested, while in small intestinal fractions, the 27,000-g pellet had the highest activity (g protein)-1, degrading four out of five peptides tested. In both small intestine and colon, the cytosol had a higher percentage of total proteolytic activity degrading each of the above polypeptides and the highest insulin-degrading activity (g protein)-1. The results suggest that at pH 7.5, proteolytic activities (g protein)-1 in the fraction of subcellular organelles are much lower than those in cytosol and that cytosolic proteolytic activities degrading polypeptides and analogues are significant.
authors: College of Pharmacy, University of Minnesota, Minneapolis 55455.
authors: J P
authors: JP
authors: Bai
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003106:Colon / Q000378:metabolism* / Q000648:ultrastructure; D003600:Cytosol / Q000378:metabolism; D013007:Growth Hormone-Releasing Hormone / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D007421:Intestine, Small / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008861:Microsomes / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D008969:Molecular Sequence Data; D009496:Neurotensin / Q000031:analogs & derivatives / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014018:Tissue Distribution
chemical_list: D007328:Insulin; D010446:Peptide Fragments; D009496:Neurotensin; C034659:acetylneurotensin (8-13); D013007:Growth Hormone-Releasing Hormone; C059148:somatotropin releasing hormone (1-29)