Laboratory of X-Ray Crystallography, Institute for Enzyme Research, University of Tokushima, Tokushima 770-8503, Japan.
Proc Natl Acad Sci U S A. 2013 Sep 3;110(36):14628-33. doi: 10.1073/pnas.1306939110. Epub 2013 Aug 19.
N-glycosylation is a major posttranslational modification that endows proteins with various functions. It is established that N-glycans are essential for the correct folding and stability of some enzymes; however, the actual effects of N-glycans on their activities are poorly understood. Here, we show that human α-l-iduronidase (hIDUA), of which a dysfunction causes accumulation of dermatan/heparan sulfate leading to mucopolysaccharidosis type I, uses its own N-glycan as a substrate binding and catalytic module. Structural analysis revealed that the mannose residue of the N-glycan attached to N372 constituted a part of the substrate-binding pocket and interacted directly with a substrate. A deglycosylation study showed that enzyme activity was highly correlated with the N-glycan attached to N372. The kinetics of native and deglycosylated hIDUA suggested that the N-glycan is also involved in catalytic processes. Our study demonstrates a previously unrecognized function of N-glycans.
N-糖基化是一种重要的翻译后修饰，赋予蛋白质各种功能。已经确定 N-聚糖对于某些酶的正确折叠和稳定性至关重要；然而，N-聚糖对其活性的实际影响还知之甚少。在这里，我们表明，人类α-L-艾杜糖苷酸酶（hIDUA）的功能障碍会导致硫酸皮肤素/肝素的积累，从而导致黏多糖贮积症 I，其自身的 N-聚糖作为底物结合和催化模块。结构分析表明，与 N372 结合的 N-聚糖中的甘露糖残基构成了底物结合口袋的一部分，并与底物直接相互作用。糖基化研究表明，酶活性与附着在 N372 上的 N-聚糖高度相关。天然和去糖基化的 hIDUA 的动力学表明，N-聚糖也参与了催化过程。我们的研究证明了 N-聚糖的一个以前未被认识的功能。
