Solubilization and structural determination of a glycoconjugate which isassembled into the sheath of Leptothrixcholodnii
Solubilization and structural determination of a glycoconjugate which isassembled into the sheath of Leptothrixcholodnii
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组装到细丝菌鞘中的糖复合物的溶解和结构测定
DOI：
10.1016/j.ijbiomac.2009.12.006
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Takeda;M.;Kondo;K.;Yamada;M.;Koizumi;J.;Mashima;T.;Matsugami;A. and Katahira;M.
肖氏纤发菌的鞘由结构糖缀合物构成，所述结构糖缀合物是用甘氨酸和半胱氨酸修饰的直链两性杂多糖。虽然聚糖核心的结构已经确定，但其与氨基酸和其他分子的修饰还没有完全解决。在这项研究中，我们的目的是确定作为一个整体的糖缀合物的化学结构。进行鞘中半胱氨酸的对映体测定，结果检测到l-半胱氨酸。NMR光谱法用于确定糖缀合物的总体结构。在NMR分析之前，通过添加变性试剂或通过衍生化来尝试糖缀合物的溶解。就所测试的而言，通过过甲酸氧化的磺化适合于增溶，但通过N-乙酰化实现了进一步的改进。用分子排阻色谱法测得其分子量约为4.5 × 104。对磺化糖缀合物及其N-乙酰化衍生物的NMR研究表明，鞘糖缀合物是由五糖重复单元组成的糖胺聚糖，所述五糖重复单元用3-羟基丙酸亚化学计量酯化并用乙酸和甘氨酰-L-半胱氨酸化学计量酰胺化。
The sheath of Leptothrix cholodnii is constructed from a structural glycoconjugate, a straight-chained amphoteric heteropolysaccharide modified with glycine and cysteine. Though the structure of the glycan core is already determined, its modifications with amino acids and other molecules are not fully resolved. In this study, we aimed to determine the chemical structure of the glycoconjugate as a whole. Enantiomeric determination of cysteine in the sheath was performed and as a result, l-cysteine was detected. NMR spectroscopy was endeavored to determine overall structure of the glycoconjugate. Prior to NMR analysis, solubilization of the glycoconjugate was attempted by adding denaturing reagents or by derivatization. As far as tested, sulfonation by performic acid oxidation was suitable for solubilization, but further improvement was achieved by N-acetylation. The approximate molecular weight of the derivative was estimated to be 4.5×104by size-exclusion chromatography. The NMR studies for the sulfonated glycoconjugate and its N-acetylated derivative revealed that the sheath glycoconjugate is a glycosaminoglycan consisting of a pentasaccharide repeating unit which is substoichiometrically esterified with 3-hydroxypropionic acid and stoichiometrically amidated with acetic acid and glycyl-l-cysteine.