O-glycosylation is probably one of the most varied sets of post-translational modifications across all organisms, but amongst the most refractory to analyze. In animals, O-xylosylation of serine residues represents the first stage in the synthesis of glycosaminoglycans, whose repeat regions are generally analyzed as fragments resulting from enzymatic or chemical degradation, whereas their core regions can be isolated by β-elimination or endo-β-xylosidase digestion. In the present study, we show that hydrazinolysis can be employed for release of glycosaminoglycan-type oligosaccharides from nematodes prior to fluorescent labeling with 2-aminopyridine. While various [HexNAcHexA]_nGal₂Xyl oligosaccharides were isolated from the model organism Caenorhabditis elegans, more unusual glycosaminoglycan-type glycans were found to be present in the porcine parasite Oesophagostomum dentatum. In this case, as judged by MS/MS before and after hydrofluoric acid or β-galactosidase digestion, core sequences with extra galactose and phosphorylcholine residues were detected as [(±PC)HexNAcHexA]_n(±PC)Galβ3-(±Galβ4)Galβ4Xyl. Thus, hydrazinolysis and fluorescent labeling can be combined to analyze unique forms of O-xylosylation, including new examples of zwitterionic glycan modifications.

中文翻译：

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寄生线虫 Oesophagostomum dentatum 合成不寻常的类糖胺聚糖 O-聚糖

O-糖基化可能是所有生物体中变化最大的一组翻译后修饰，但也是最难分析的。在动物中，丝氨酸残基的 O-木糖基化代表糖胺聚糖合成的第一阶段，其重复区域通常被分析为酶促或化学降解产生的片段，而它们的核心区域可以通过 β-消除或内切-β- 分离木糖苷酶消化。在本研究中，我们表明在用 2-氨基吡啶进行荧光标记之前，肼解作用可用于从线虫中释放糖胺聚糖型寡糖。虽然从模式生物秀丽隐杆线虫中分离出各种 [HexNAcHexA] _n Gal _{2 Xyl 寡糖}, 更不寻常的糖胺聚糖型聚糖被发现存在于猪寄生虫Oesophagostomum dentatum中。在这种情况下，根据氢氟酸或 β-半乳糖苷酶消化前后的 MS/MS 判断，检测到具有额外半乳糖和磷酸胆碱残基的核心序列为 [(±PC)HexNAcHexA] n (±PC)Galβ3-(± _Galβ4 ) Galβ4Xyl。因此，可以结合肼解和荧光标记来分析独特形式的 O-木糖基化，包括两性离子聚糖修饰的新例子。