Biosynthesis of intestinal microvillar proteins. Pulse-chase labelling studies on maltase-glucoamylase, aminopeptidase A and dipeptidyl peptidase IV
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The biogenesis of three intestinal microvillar enzymes, maltase-glucoamylase (EC 3.2.1.20), aminopeptidase A (aspartate aminopeptidase, EC 3.4.11.7) and dipeptidyl peptidase IV (EC 3.4.14.5), was studied by pulse-chase labelling of pig small-intestinal explants kept in organ culture. The earliest detectable forms of the enzymes were polypeptides of Mr 225000, 140000 and 115000 respectively. These were found to represent the enzymes in a 'high-mannose' state of glycosylation, as judged by their susceptibility to treatment with endo-beta-N-acetylglucosaminidase H (EC 3.2.1.96). After about 40-60 min of chase, maltase-glucoamylase, aminopeptidase A and dipeptidyl peptidase IV were further modified to yield the mature polypeptides of Mr 245000, 170000 and 137000 respectively, which were expressed at the microvillar membrane after 60-90 min of chase. The fact that the enzymes before reaching the microvillar membrane were found in a Ca2+-precipitated membrane fraction (intracellular and basolateral membranes), but not in soluble form, indicates that during biogenesis maltase-glucoamylase, aminopeptidase A and dipeptidyl peptidase IV are transported and assembled in a membrane-bound state.
Original language | English |
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Journal | Biochemical Journal |
Volume | 210 |
Issue number | 2 |
Pages (from-to) | 389-93 |
Number of pages | 4 |
ISSN | 0264-6021 |
Publication status | Published - 1983 |
Bibliographical note
Keywords: Acetylglucosaminidase; Aminopeptidases; Animals; Dipeptidyl Peptidases; Electrophoresis, Polyacrylamide Gel; Endopeptidases; Glucan 1,4-alpha-Glucosidase; Glucosidases; Glutamyl Aminopeptidase; Intestine, Small; Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; Membrane Proteins; Microvilli; Organ Culture Techniques; Swine
ID: 9881420