POST-BIOSYNTHETIC MODIFICATION OF HEPARAN SULFATE BY REACTIVE NITROGEN SPECIES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 细胞表面和细胞外基质上的硫酸乙酰肝素(HS)链受酶和化学物质的作用而改变其生物活性。活性氮物种(RNS)为维管组织中HS链的脱氨基断裂提供了条件。这样释放出来的含醛HS链很可能对细胞蛋白质起反应。为阐明这些机制而进行的结构调查是本项目的主题。 我们使用质谱糖平台的结果表明，存在一种结构(？六-GlcNH26S)的双糖。这些结果与六-GlcNH26S对应的HS重复序列的存在是一致的，这些重复序列是用其他方法无法检测到的。具有游离氨基的双糖很可能很难用标准的双糖分析方法检测出来，因为它的两性离子性质导致它在离子交换树脂上的保留率很差，或者与离子配对剂配对很弱。 成熟HS链上含有游离氨基的二糖单元的存在似乎与N-脱乙酰酶/N-磺基转移酶的作用机制和3‘-磷酸腺苷-5’-磷酸硫酸盐的可用性有关。我们的工作表明，含有六-GlcNH26S的双糖单位在器官组织中广泛表达。含有二糖单元的HS链很容易受到NO介导的切割，就像Glypcan-1环化所描述的那样。NO介导的切割条件可能存在于其他生物过程中。众所周知，HS的氨基葡萄糖在可能出现炎症的条件下，会与氧化剂如HOCl迅速反应。显然，Six-GlcNH26S重复序列是一种广泛表达和功能相关的HS亚结构。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Heparan sulfate (HS) chains on cell surfaces and in extracellular matrices are acted upon by enzymes and chemical species to alter their biological activities. Reactive nitrogen species (RNS) give rise to conditions for deaminative cleavage of HS chains in vascular tissue. It is likely that aldehyde-containing HS chains so liberated become reactive toward cellular proteins. Structural investigations to elucidate these mechanisms are the subject of this project. Our results using a mass spectrometry glycomics platform show the presence of a disaccharide of structure (¿HexA-GlcNH26S). These results are consistent with the presence of HS repeats corresponding to HexA-GlcNH26S that are not detectable using other methods. It is likely that disaccharides with free amino groups are difficult to detect using standard disaccharide analysis methods because its zwitterionic nature causes poor retention on ion exchange resins or weak pairing with ion-pairing agents. The presence of disaccharide units containing free glucosamine amino groups in mature HS chains seems to be related to the mechanisms of action of N-deacetylase/N-sulfotransferase enzymes and the availability of 3'-phosphoadenosine-5'-phosphosulfate. Our work shows that disaccharide units containing HexA-GlcNH26S are widely expressed in organ tissue. HS chains containing such disaccharide units would be susceptible to NO-mediated cleavage as has been described for glypican-1 cycling. Conditions for NO-mediated cleavage may exist in other biological processes. Glucosamine amino groups of HS are also known to react rapidly with oxidizing agents such as HOCl under conditions that are likely to be present at inflammation. It is clear that the HexA-GlcNH26S repeat is a widely expressed and functionally relevant HS sub-structure.