Oxidation of glycosphingolipids under basic conditions: synthesis of glycosyl "serine acids" as opposed to "ceramide acids". Precursors for neoglycoconjugates with increased ligand binding affinity.
Oxidation of glycosphingolipids under basic conditions: synthesis of glycosyl "serine acids" as opposed to "ceramide acids". Precursors for neoglycoconjugates with increased ligand binding affinity.
复制标题
碱性条件下鞘糖脂的氧化：合成糖基“丝氨酸”而不是“神经酰胺酸”。
DOI：
10.1021/bi990669m
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Lingwood,CA
中科院分区：
文献类型：
--
作者：
Mylvaganam,M;Meng,L;Lingwood,CA
描述了鞘糖脂（GSL）双键的两种类型的氧化裂解。用化学计量比例的KMnO 4和过量的NaIO 4在中性水-叔丁醇溶剂体系中氧化全乙酰化的GSL前体，得到几乎定量的糖基神经酰胺酸、2-羟基-3-（N-酰基）-4-（O-糖基）氧基丁酸[Mylvaganam，M.，和Lingwood，C. A.（1999）J.Biol.Chem.274，20725 - 20732]。然而，如果使反应介质呈碱性，则鞘脂的羟基烯丙基官能团作为整体被氧化，并且以良好的产率获得糖基丝氨酸、2-（N-酰基）-3-（O-糖基）氧基丙酸。这是一种新型的氧化反应。优化的条件下得到糖基神经酰胺或丝氨酸，具有大于90%的选择性和良好的产率（90%）。dGSL的氧化得到丝氨酸和神经酰胺寡糖，缺乏烃链。通过ESMS分析鉴定了一种有趣的糖基物质，含有5-羟基-4-氧代-3-羟基-2-（N-酰基）鞘氨醇（羟基-酰基中间体）。我们建议，该中间体的进一步氧化是pH值依赖性的，将被氧化为丝氨酸或神经酰胺酸。基于丝氨酸和神经酰胺酸的特定同系物的MS-MS分析，已经建立了两种类型的碰撞诱导解离（CID）模式。这些CID模式，然后用于鉴定的丝氨酸和神经酰胺酸合成的天然GSL样品。此外，在定性的基础上，该氧化方案，结合ESMS，提供了一种新的方法，用于表征糖苷配基组成（酰基链长，不饱和位置，二氢鞘氨醇含量等）。天然GSL通过将酸偶联到刚性烃框架如2-氨基金刚烷上，合成了一类新的烃缀合物。对来自三己糖基神经酰胺（Gb 3C）、乳糖基神经酰胺（LC）和半乳糖基神经酰胺（GalC）的缀合物的初步研究以预期的特异性结合verotoxin，但亲和力远大于天然糖脂。此外，基于神经酰胺酸的缀合物是比丝氨酸缀合物更好的配体。
Two types of oxidative cleavage of the double bond of glycosphingolipids (GSLs) are described. Oxidation of peracetylated GSL precursors with stoichiometric proportions of KMnO4and an excess of NaIO4, in a neutral aqueoustert-butanol solvent system, gave nearly quantitative yields of the glycosyl ceramide acid, 2-hydroxy-3-(N-acyl)-4-(O-glycosyl)oxybutyric acid [Mylvaganam, M., and Lingwood, C. A. (1999)J. Biol. Chem.274, 20725−20732]. However, if the reaction medium was made alkaline, the hydroxyallylic function of the sphingolipid, as a whole, was oxidized and the glycosyl serine acid, 2-(N-acyl)-3-(O-glycosyl)oxypropionic acid, was obtained in good yield. This represents a new type of oxidation reaction. Optimized conditions gave glycosyl ceramide or serine acids with greater than 90% selectivity and in good yields (90%). Oxidation of dGSLs gave serine and ceramide oligosaccharides, devoid of hydrocarbon chains. An intriguing glycosyl species containing 5-hydroxy-4-oxo-3-hydroxy-2-(N-acyl)sphingosine (hydroxy−acyl intermediate) was identified via ESMS analyses. We propose that further oxidation of this intermediate is pH-dependent and will be oxidized to either serine or ceramide acids. On the basis of MS−MS analysis of specific homologues of serine and ceramide acids, two types of collision-induced dissociation (CID) patterns have been established. These CID patterns were then used in the identification of serine and ceramide acids synthesized from natural GSL samples. Also, on a qualitative basis, this oxidation protocol, in conjunction with ESMS, provides a novel method for characterizing the aglycone composition (acyl chain length, unsaturation position, dihydrosphingosine content, etc.) of natural GSLs. A novel class of neohydrocarbon conjugates were synthesized by coupling the acids to rigid hydrocarbon frames such as 2-aminoadamantane. Preliminary studies with conjugates derived from globotriaosyl ceramide (Gb3C), lactosyl ceramide (LC), and galactosyl ceramide (GalC) bound verotoxin with the expected specificity but with affinities much greater than that of the natural glycolipid. Also, the ceramide acid-based conjugates were better ligands than serine acid conjugates.