Processing of iduronate 2-sulphatase in human fibroblasts.
Processing of iduronate 2-sulphatase in human fibroblasts.
复制标题
人成纤维细胞中艾杜糖醛酸 2-硫酸酯酶的加工。
作者：
R. Froissart;G. Millat;M. Mathieu;D. Bozon;I. Maire
艾杜糖酸2-硫酸酯酶(IDs)是一种参与降解硫酸皮肤素和硫酸乙酰肝素的溶酶体酶。通过纯化胎盘IDs(A型和B型)或在大肠杆菌中表达三种不同的融合多肽来获得抗原性材料，从而产生五种特异性抗体。在高表达成纤维细胞中的脉冲追逐标记实验表明，入侵检测系统处理不佳，但大量前体被分泌到培养液中。缺失的成纤维细胞对35S或33P标记的前体细胞的内吞作用，以及亮肽素对糖基化和蛋白分解的抑制作用，可以更好地阐明IDS的成熟。在高尔基体中，最初的73-78 kDa形式在其寡糖链被修饰后被转化为磷酸化的90 kDa前体。这种前体通过各种中间体被蛋白水解酶切割成一个主要的55 kDa中间体，并释放出一个18 kDa的多肽。进一步的蛋白水解酶裂解得到45 kDa的成熟形式，包含杂合型和复合型寡糖链。
Iduronate 2-sulphatase (IDS) is a lysosomal enzyme involved in degradation of dermatan sulphate and heparan sulphate. Antigenic material was obtained either by purification of placental IDS (A and B forms) or by expression of three different fusion peptides in Escherichia coli allowing the production of five specific antibodies. Pulse-chase-labelling experiments in over-expressing fibroblasts showed poor IDS processing but large amounts of precursors were secreted into the medium. The endocytosis of the 35S- or 33P-labelled precursors by deleted fibroblasts together with glycosylation studies and proteolysis inhibition by leupeptin allowed better elucidation of IDS maturation. The initial 73-78 kDa form is converted into a phosphorylated 90 kDa precursor after modification of its oligosaccharide chains in the Golgi apparatus. This precursor is processed by proteolytic cleavage through various intermediates to a major 55 kDa intermediate, with the release of an 18 kDa polypeptide. Further proteolytic cleavage by a thiol protease gives the 45 kDa mature form containing hybrid and complex-type oligosaccharide chains.