title: Biosynthesis of intestinal microvillar proteins. The effect of swainsonine on post-translational processing of aminopeptidase N.
abstract: The post-translational processing of pig small-intestinal aminopeptidase N (EC 3.4.11.2) was studied in organ-cultured mucosal explants. Exposure of the explants to swainsonine, an inhibitor of Golgi mannosidase II, resulted in the formation of a Mr-160000 polypeptide, still sensitive to endo-beta-N-acetylglucosaminidase H. Swainsonine caused only a moderate inhibition of transport of the enzyme through the Golgi complex and the subsequent expression in the microvillar membrane. This may imply that the trimming of the high-mannose core and complex glycosylation of N-linked oligosaccharides is not essential for the transport of aminopeptidase N to its final destination. A different type of processing was observed to take place in the presence of swainsonine, resulting in a considerable increase in apparent Mr (from 140000 to 160000). This processing could not be ascribed to N-linked glycosylation, since treatment of the Mr-160000 polypeptide with endo-beta-N-acetylglucosaminidase H only decreased its apparent Mr by 15000. The susceptibility of the mature Mr-166000 polypeptide, but not the Mr-140000 polypeptide, to mild alkaline hydrolysis suggests that aminopeptidase N becomes glycosylated with O-linked oligosaccharides during its passage through the Golgi complex. Aminopeptidase N was not labelled by [3H]palmitic acid, indicating that the processing of the enzyme does not include acylation.
mesh_terms: D000118:Acetylglucosaminidase / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology*; D000626:Aminopeptidases / Q000096:biosynthesis* / Q000378:metabolism; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D018826:CD13 Antigens; D004591:Electrophoresis, Polyacrylamide Gel; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology*; D037102:Lectins; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D008871:Microvilli / Q000187:drug effects / Q000201:enzymology; D009924:Organ Culture Techniques; D037121:Plant Lectins; D011499:Protein Processing, Post-Translational / Q000187:drug effects*; D017026:Swainsonine; D013552:Swine
chemical_list: D000470:Alkaloids; D037102:Lectins; D037121:Plant Lectins; C017707:Ricinus communis agglutinin-1; D000118:Acetylglucosaminidase; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D000626:Aminopeptidases; D018826:CD13 Antigens; D017026:Swainsonine