Ketone isosteres of 2-N-acetamidosugars as substrates for metabolic cell surface engineering
Ketone isosteres of 2-N-acetamidosugars as substrates for metabolic cell surface engineering
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DOI：
10.1021/ja002962b
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发表时间：
2001-02-14
影响因子：
15
通讯作者：
Bertozzi, CR
中科院分区：
文献类型：
--
作者：
Hang, HC;Bertozzi, CR
使用非天然底物的代谢寡糖工程为在细胞表面引入新型化学反应性提供了途径。 1 这种方法利用了参与碳水化合物生物合成的酶的非自然底物耐受性（如图 1A 所示）。例如，N-乙酰甘露糖胺（ManNAc）的衍生物，其在N-酰基上带有选择性反应性化学手柄，例如酮2或叠氮化物3，被人类细胞转化为糖缀合物结合的唾液酸苷。酮与氨氧基或酰肼基团以及叠氮化物与改性膦试剂的选择性反应性，允许外源化学细胞表面靶向。 4 如果唾液酸途径的酶和转运蛋白所表现出的底物混杂性是其他碳水化合物代谢途径的普遍特征，那么代谢工程的多种途径将是可用的。到目前为止，很少有研究解决其他碳水化合物生物合成途径的非自然底物耐受性。 1糖蛋白、蛋白聚糖和糖脂中普遍存在 2-N-乙酰胺糖、5 N-乙酰氨基葡萄糖 (GlcNAc) 和 N-乙酰半乳糖胺 (Gal-NAc)，这使得它们成为代谢工程的有吸引力的目标。 GlcNAc 和 GalNAc 在细胞内通过补救途径转化为 UDP 激活的类似物。 6 UDP-GlcNAc 随后可转化为 ManNAc 或 UDP-GalNAc，或被 GlcNAc 转移酶利用，将糖掺入各种糖复合物中。同样，GalNAc 转移酶利用 UDP-GalNAc 作为底物，并将糖递送至多种糖复合物。我们考虑了非天然 GlcNAc 和 GalNAc 衍生物可能通过各自的补救途径进入细胞表面的可能性。我们设计了“2-酮糖”，它是 2-N-乙酰胺糖的 C2-碳等排体（图 1B），作为具有酮基的新型类似物，可与氨氧基或酰肼试剂发生化学选择性反应。 2-酮糖的简明合成是从已知的2-碘糖开发出来的，2-碘糖很容易通过市售糖醛的亲电碘化获得。 7
Metabolic oligosaccharide engineering using unnatural substrates has provided an avenue for the introduction of novel chemical reactivity on cell surfaces. 1 This approach exploits the unnatural substrate tolerance of enzymes involved in carbohydrate biosynthesis (depicted schematically in Figure 1A). For example, derivatives of N-acetylmannosamine (ManNAc) which bear a selectively reactive chemical handle, such as a ketone2 or azide, 3 on the N-acyl group are transformed into glycoconjugate-bound sialosides by human cells. The selective reactivity of ketones with aminooxy or hydrazide groups, and azides with modified phosphine reagents, permits exogenous chemical cell surface targeting. 4 If the substrate promiscuity exhibited by the enzymes and transporters of the sialic acid pathway is a general feature of other carbohydrate metabolic pathways, multiple avenues for metabolic engineering will be available. So far, few studies have addressed the unnatural substrate tolerance of other carbohydrate biosynthetic pathways. 1The ubiquitous presence of the 2-N-acetamidosugars, 5 N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (Gal-NAc), in glycoproteins, proteoglycans, and glycolipids makes them attractive targets for metabolic engineering. GlcNAc and GalNAc are converted within cells to their UDP-activated analogues via salvage pathways. 6 UDP-GlcNAc can be subsequently converted to ManNAc or UDP-GalNAc, or utilized by GlcNAc transferases that incorporate the sugar into various glycoconjugates. Likewise, GalNAc transferases utilize UDP-GalNAc as a substrate and deliver the sugar to numerous glycoconjugates. We considered the possibility that unnatural GlcNAc and GalNAc derivatives might gain access to the cell surface through their respective salvage pathways. We designed “2-ketosugars”, which are C2-carbon isosteres of the 2-N-acetamidosugars (Figure 1B), as novel analogues that possess a ketone group for chemoselective reaction with aminooxy or hydrazide reagents. A concise synthesis of 2-ketosugars was developed from known 2-iodosugars, which are readily available by electrophilic iodination of commerically available glycals. 7