Chemoenzymatic synthesis of hydrophobic glycoprotein: synthesis of saposin C carrying complex-type carbohydrate.
Chemoenzymatic synthesis of hydrophobic glycoprotein: synthesis of saposin C carrying complex-type carbohydrate.
复制标题
DOI：
10.1021/jo3010155
复制
发表时间：
2012-07
期刊：
影响因子：
--
通讯作者：
H. Hojo;Hiromasa Tanaka;M. Hagiwara;Yuya Asahina;A. Ueki;H. Katayama;Y. Nakahara;Azusa Yoneshige;J. Matsuda;Yukishige Ito;Y. Nakahara
中科院分区：
文献类型：
--
作者：
H. Hojo;Hiromasa Tanaka;M. Hagiwara;Yuya Asahina;A. Ueki;H. Katayama;Y. Nakahara;Azusa Yoneshige;J. Matsuda;Yukishige Ito;Y. Nakahara
使用苄基保护的 LacNAc、甘露糖和 β-甘露糖基 GlcNAc 单元作为关键构建块，有效合成了以 LacNAc 作为非还原端糖的复合型 N-连接八糖恶唑啉。为了实现 LacNAc 单元的高度 β-选择性糖基化，使用 N-三氯乙酰基来保护 LacNAc 单元中的氨基。这些单元完成组装并脱保护后，所得游离糖成功衍生化为相应的糖恶唑啉。另一方面，N-乙酰葡糖胺化saposin C（一种疏水性脂质结合蛋白）是通过天然化学连接反应化学合成的。在之前与非糖基化saposin C合成相关的结果的基础上，将O-酰基异肽结构引入到携带GlcNAc的N端肽硫酯中，以提高其对水性有机溶剂的溶解度。连接反应有效地进行，同时 O-酰基异肽部分处的 O-酰基转移至 N-酰基。去除半胱氨酸保护基并折叠后，成功获得携带GlcNAc的saposin C。然后利用来自毛霉的内切-β-N-乙酰氨基葡萄糖苷酶（Endo-M）（糖合酶）突变体将合成的糖恶唑啉转移到该糖蛋白上，成功获得携带复合型九糖的saposin C。
The complex-type N-linked octasaccharide oxazoline having LacNAc as the nonreducing end sugar was efficiently synthesized using the benzyl-protected LacNAc, mannose, and β-mannosyl GlcNAc units as key building blocks. To achieve a highly β-selective glycosylation with the LacNAc unit, the N-trichloroacetyl group was used for the protection of the amino group in the LacNAc unit. After complete assembly of these units and deprotection, the obtained free sugar was successfully derivatized into the corresponding sugar oxazoline. On the other hand, the N-acetylglucosaminylated saposin C, a hydrophobic lipid-binding protein, was chemically synthesized by the native chemical ligation reaction. On the basis of the previous results related to the synthesis of the nonglycosylated saposin C, the O-acyl isopeptide structure was introduced to the N-terminal peptide thioester carrying GlcNAc to improve its solubility toward aqueous organic solvents. The ligation reaction efficiently proceeded with the simultaneous O- to N-acyl shift at the O-acyl isopeptide moiety. After the removal of the cysteine-protecting group and folding, saposin C carrying GlcNAc was successfully obtained. The synthetic sugar oxazoline was then transferred to this glycoprotein using the mutant of endo-β-N-acetylglucosaminidase from Mucor hiemalis (Endo-M) (glycosynthase), and the saposin C carrying the complex-type nonasaccharide was successfully obtained.