Autocatalytic polysialylation of polysialyltransferase-1
Autocatalytic polysialylation of polysialyltransferase-1
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DOI：
10.1002/j.1460-2075.1996.tb01086.x
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发表时间：
1996-12-16
期刊：
影响因子：
11.4
通讯作者：
GerardySchahn, R
中科院分区：
文献类型：
--
作者：
Muhlenhoff, M;Eckhardt, M;GerardySchahn, R
聚唾液酸(PSA)是神经细胞黏附分子NCAM的一种特异和高度调控的翻译后修饰，PSA的合成依赖于最近从三种哺乳动物中克隆的单个酶--多唾液酸转移酶-1(PST-1)的活性。本研究探讨了PST-1的催化机制，利用新开发的体外检测系统，我们证明了PST-1的自聚唾液酸化，即与活化的糖供体CMP-Neu5Ac接触后立即合成涉及N-糖基化位点的PSA链，而不是NCAM，Neu5Ac的多唾液酸化如果需要在α2，3或α2，6位置进行末端唾液酸化，则可以在从Lec2互补组的CHO细胞分离的asialo-PST-1中开始自聚唾液酸化。预先形成的PSA链不转移到NCAM。然而，自催化步骤很可能是酶活性的先决条件，因为从Lec8细胞中分离的无糖PST-1在功能上是无效的，我们的数据描述了糖基转移酶自催化成熟的新途径，从而为旨在阐明和影响PST-1催化功能的研究提供了新的基础。
Polysialic acid (PSA) is a specific and highly regulated post-translational modification of the neural cell adhesion molecule NCAM, Synthesis of PSA depends on the activity of a single enzyme, the polysialyltransferase-1 (PST-1), recently cloned from three mammalian species, The present study was carried out to investigate the catalytic mechanism of PST-1, Using a newly developed in vitro assay system, we demonstrate autopolysialylation for PST-1, The synthesis of PSA chains, which involved N-glycosylation sites, occurred immediately after contact with the activated sugar donor CMP-Neu5Ac, In contrast to the polysialylation of NCAM, where terminal sialylation in either the alpha 2,3 or alpha 2,6 position is required, the autopolysialylation could be started in the asialo-PST-1 isolated from CHO cells of the Lec2 complementation group. Pre-formed PSA chains were not transferred to NCAM. Nevertheless, the autocatalytic step is likely to be a prerequisite for enzymatic activity, since agalacto-PST-1 isolated from Lec8 cells was functionally inactive, Our data describe a novel route of autocatalytic maturation of a glycosyltransferase and thereby provide a new basis for studies aimed at elucidating and influencing the catalytic functions of PST-1.