Distribution of iduronate 2-sulphate residues in heparan sulphate. Evidence for an ordered polymeric structure.
Distribution of iduronate 2-sulphate residues in heparan sulphate. Evidence for an ordered polymeric structure.
复制标题
硫酸乙酰肝素中艾杜糖醛酸 2-硫酸酯残基的分布。
作者：
J. Turnbull;J. Gallagher
已通过用肝素酶解聚来检查人皮肤成纤维细胞硫酸乙酰肝素的结构，肝素酶特异性切割结构为GlcNSO 3（+/-6S）-α 1，4 IdoA（2S）[N-硫酸化葡糖胺（6-硫酸盐）-α 1，4-艾杜糖醛酸2-硫酸盐]的高度硫酸化二糖。硫酸乙酰肝素仅含有一小部分（约10%）对这种酶敏感的连接。肝素酶解聚的主要产物是平均分子量为10 kDa的大寡糖（dp约为40，其中dp为聚合度;对于二糖，dp = 2等）。如通过SepharoseCL-6 B上的凝胶过滤所评估的，与完整链的45 kDa（dp约200）的分子量相比。大的肝素酶抗性寡糖对肝素酶解聚高度敏感，肝素酶在低硫酸化区域切割硫酸乙酰肝素，其中N-乙酰化二糖[GlcNAc-α 1，4GlcA（N-乙酰葡糖胺基-α 1，4-葡萄糖醛酸）]是主要结构单元。肝素酶切割位点位置的进一步分析表明，它们主要发现于平均长度为4 - 7个二糖（dp 8- 1,4）的GlcNSO 3-α 1，4 IdoA重复序列的中心位置。这些结果表明，肝素酶在大约四个或五个N-硫酸化结构域中切割硫酸乙酰肝素，每个结构域包含两个或三个敏感双糖的簇;这些结构域被富含N-乙酰基的长序列分开，这些序列明显缺乏硫酸基团。在这些研究结果的基础上，提出了一个模型，它描绘了硫酸乙酰肝素作为一个有序的聚合物结构组成的交替排列的硫酸盐丰富和硫酸盐贫乏的地区。富含硫酸根的区域可能是链的柔性区域，因为它们的构象多功能IdoA和IdoA（2S）残基含量高。该模型对硫酸乙酰肝素的生物合成和功能具有重要意义。
The structure of human skin fibroblast heparan sulphate has been examined by depolymerization with heparinase, which specifically cleaves highly sulphated disaccharides of structure GlcNSO3 (+/-6S)-alpha 1,4IdoA(2S) [N-sulphated glucosamine (6-sulphate)-alpha 1,4-iduronic acid 2-sulphate]. Heparan sulphate contained only a small proportion (approximately 10%) of linkages susceptible to this enzyme. The major products of depolymerization with heparinase were large oligosaccharides with an average molecular mass of 10 kDa (dp approximately 40, where dp is degree of polymerization; for disaccharides, dp = 2 etc.) as assessed by gel filtration on Sepharose CL-6B, compared with a molecular mass of 45 kDa (dp approximately 200) for the intact chains. The large heparinase-resistant oligosaccharides were highly susceptible to depolymerization with the enzyme heparitinase, which cleaves heparan sulphate in areas of low sulphation, where N-acetylated disaccharides [GlcNAc-alpha 1,4GlcA (N-acetylglucosaminyl-alpha 1,4-glucuronic acid)] are the predominant structural unit. Further analysis of the location of the heparinase cleavage sites indicated that they were predominantly found in a central position in GlcNSO3-alpha 1,4IdoA repeat sequences of average length four to seven disaccharides (dp 8-14). These results indicate that heparinase cleaves heparan sulphate in approximately four or five N-sulphated domains, each domain containing a cluster of two or three susceptible disaccharides; the domains are separated by long N-acetyl-rich sequences that are markedly deficient in sulphate groups. On the basis of these findings a model is proposed which depicts heparan sulphate as an ordered polymeric structure composed of an alternate arrangement of sulphate-rich and sulphate-poor regions. The sulphate-rich regions are likely to be flexible areas of the chain because of their high content of the conformationally versatile IdoA and IdoA(2S) residues. The model has important implications for the biosynthesis and functions of heparan sulphate.