硫酸角质素(KS)是一种蛋白聚糖,在各种组织类型的细胞外基质中广泛表达,它执行多种生物学功能。KS是最不了解的蛋白聚糖,这部分是由于缺乏结构结合研究所需的定义明确的KS寡糖,作为分析标准,检查角蛋白酶的底物特异性,和药物开发。这里,我们报告了一种仿生方法,可以安装,以区域选择性的方式,通过使用特定的酶模块,在寡N-乙酰基乳糖胺(LacNAc)链上的硫酸盐和岩藻糖苷提供KS的任何结构元件。基于观察到α1,3-岩藻苷,α2,6-唾液酸苷和半乳糖(Gal6S)的C-6硫酸化是相互排斥的,并且不能发生在相同的LacNAc部分上。因此,半乳糖苷的硫酸化模式可以通过安装α1,3-岩藻苷或α2,6-唾液酸苷来控制,以暂时阻断某些LacNAc部分被硫酸角质素半乳糖6-磺基转移酶(CHST1)硫酸化。α1,3-岩藻糖基化和α2,6-唾液酸化的模式可以通过利用这些修饰的相互排他性来控制,它又控制了CHST1的硫酸化位点。用岩藻糖苷酶或唾液酸酶去除阻断岩藻苷或唾液酸苷的后期处理提供选择性硫酸化KS寡糖。这些处理还为CHST1的进一步修饰揭开了特定的半乳糖苷。为了展示酶促策略的潜力,我们已经制备了一系列具有不同岩藻糖基化和硫酸化模式的聚LacNAc衍生物和由硫酸盐的特定排列修饰的几种N-聚糖。
Keratan sulfate (KS) is a proteoglycan that is widely expressed in the extracellular matrix of various tissue types, where it performs multiple biological functions. KS is the least understood proteoglycan, which in part is due to a lack of panels of well-defined KS oligosaccharides that are needed for structure-binding studies, as analytical standards, to examine substrate specificities of keratinases, and for drug development. Here, we report a biomimetic approach that makes it possible to install, in a regioselective manner, sulfates and fucosides on oligo-N-acetyllactosamine (LacNAc) chains to provide any structural element of KS by using specific enzyme modules. It is based on the observation that α1,3-fucosides, α2,6-sialosides and C-6 sulfation of galactose (Gal6S) are mutually exclusive and cannot occur on the same LacNAc moiety. As a result, the pattern of sulfation on galactosides can be controlled by installing α1,3-fucosides or α2,6-sialosides to temporarily block certain LacNAc moieties from sulfation by keratan sulfate galactose 6-sulfotransferase (CHST1). The patterns of α1,3-fucosylation and α2,6-sialylation can be controlled by exploiting the mutual exclusivity of these modifications, which in turn controls the sites of sulfation by CHST1. Late-stage treatment with a fucosidase or sialidase to remove blocking fucosides or sialosides provides selectively sulfated KS oligosaccharides. These treatments also unmasked specific galactosides for further modification by CHST1. To showcase the potential of the enzymatic strategy, we have prepared a range of poly-LacNAc derivatives having different patterns of fucosylation and sulfation and several N-glycans decorated by specific arrangements of sulfates.