Danielsen E M, Cowell G M, Norén O, Sjöström H, Dorling P R
Biochem J. 1983 Nov 15;216(2):325-31. doi: 10.1042/bj2160325.
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.
在器官培养的黏膜外植体中研究了猪小肠氨肽酶N（EC 3.4.11.2）的翻译后加工过程。将外植体暴露于高尔基体甘露糖苷酶II的抑制剂苦马豆素中，导致形成一种Mr为160000的多肽，该多肽仍对内切β-N-乙酰葡糖胺酶H敏感。苦马豆素仅对该酶通过高尔基体复合体的转运以及随后在微绒毛膜中的表达产生适度抑制。这可能意味着高甘露糖核心的修剪和N-连接寡糖的复杂糖基化对于氨肽酶N转运至其最终目的地并非必不可少。在苦马豆素存在的情况下观察到了一种不同类型的加工过程，导致表观Mr显著增加（从140000增加到160000）。这种加工过程不能归因于N-连接糖基化，因为用内切β-N-乙酰葡糖胺酶H处理Mr为160000的多肽仅使其表观Mr降低了15000。成熟的Mr为166000的多肽（而非Mr为140000的多肽）对温和碱性水解敏感，这表明氨肽酶N在通过高尔基体复合体的过程中被O-连接寡糖糖基化。氨肽酶N未被[3H]棕榈酸标记，表明该酶的加工过程不包括酰化作用。
