CHEMICAL-ENZYMATIC SYNTHESIS AND CONFORMATIONAL-ANALYSIS OF SIALYL LEWIS-X AND DERIVATIVES
CHEMICAL-ENZYMATIC SYNTHESIS AND CONFORMATIONAL-ANALYSIS OF SIALYL LEWIS-X AND DERIVATIVES
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DOI：
10.1021/ja00050a007
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发表时间：
1992-11-18
影响因子：
15
通讯作者：
WONG, CH
中科院分区：
文献类型：
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作者：
ICHIKAWA, Y;LIN, YC;WONG, CH
已经使用β-1，4-半乳糖基转移酶和重组α-2，3-唾液酸转移酶和α-1，3-岩藻糖基转移酶合成了唾液酸刘易斯x和衍生物。酶促糖基化已经在制备规模上实现了UDP-半乳糖、CMP-N-乙酰神经氨酸和GDP-岩藻糖的原位再生。此外，半乳糖基转移酶和岩藻糖基转移酶的底物特异性和抑制方面进行了研究。酶促方法也用于合成2-脱氧-LacNAc、2 ′-氨基-2-脱氧-LacNAc、2-叠氮基-Lac、刘易斯x、GlcNAc被5-硫代葡萄糖取代的刘易斯x类似物、[Gal-1-C-13]-LacNAc、[Gal-1-C-13]-唾液酰基刘易斯x和相应的末端糖基。合成的C-13-标记的sialyl刘易斯x和中间体（包括刘易斯x和sialyl LacNAc）用于使用NMR技术结合基于GESA和MM 2程序的计算的构象研究。对唾液酸基刘易斯x进行GESA计算，得到了4种能量最低的构象，其中A和B两种构象与NMR结果一致，用MM 2计算进一步修正。具有较低能量的一个（A '）被选为优选的构象异构体，其所有的核间距和糖苷扭转角与NMR分析一致。例如，基于Gal-1-C-13和GlcNAc之间的偶联，Gal-GlcNAc的糖苷扭转角psi被确定为18度，而预测值为15度。该四糖似乎沿NeuAc-Gal-Fuc形成一个明确的亲水表面，沿着NeuAc-GlcNAc形成一个疏水表面。通过比较sialyl刘易斯x和sialyl刘易斯a的构象，发现sialyl刘易斯x的识别结构域主要来自唾液酸-半乳糖-岩藻糖残基。
Sialyl Lewis x and derivatives have been synthesized using beta-1,4-galactosyltransferase and recombinant alpha-2,3-sialyltransferase and alpha-1,3-fucosyltransferase. The enzymatic glycosylations have been achieved on preparative scales with in situ regeneration of UDP-galactose, CMP-N-acetylneuraminic acid, and GDP-fucose. Additionally, galactosyltransferase and fucosyltransferases have been studied with respect to their substrate specificity and inhibition. The enzymatic procedures have also been used in the synthesis of 2-deoxy-LacNAc, 2'-amino-2-deoxy-LacNAc, 2-azido-Lac, Lewis x, the Lewis x analog with GlcNAc replaced with 5-thioglucose, [Gal-1-C-13]-LacNAc, [Gal-1-C-13]-sialyl Lewis x, and the corresponding terminal glycal. The synthesized C-13-labeled sialyl Lewis x and intermediates (including Lewis x and sialyl LacNAc) were used for conformational study using NMR techniques combined with calculations based on GESA and MM2 programs. GESA calculation of sialyl Lewis x gave four minimum-energy conformers, and the two (A and B) consistent with NMR results were further refined with MM2 calculation. The one (A') with lower energy was picked as the preferred conformer which had all internuclear distances and glycosidic torsional angles consistent with the NMR analysis. The glycosidic torsional angle psi of Gal-GlcNAc, for example, was determined to be 18-degrees on the basis of the coupling between Gal-1-C-13 and GlcNAc, while the predicted value was 15-degrees. The tetrasaccharide appears to form a well-defined hydrophilic surface along NeuAc-Gal-Fuc, and a hydrophobic face underneath NeuAc-GlcNAc. Comparing the conformation of sialyl Lewis x to sialyl Lewis a indicates that the recognition domain of sialyl Lewis x mainly comes from the sialic acid-galactose-fucose residues.