The post-translational processing of pig small-intestinal aminopeptidase N (EC 126.96.36.199) 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.
Biosynthesis of intestinal microvillar proteins. The effect of swainsonine on post-translational processing of aminopeptidase N
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E M Danielsen, G M Cowell, O Norén, H Sjöström, P R Dorling; Biosynthesis of intestinal microvillar proteins. The effect of swainsonine on post-translational processing of aminopeptidase N. Biochem J 15 November 1983; 216 (2): 325–331. doi: https://doi.org/10.1042/bj2160325
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