Structural Study on th Carbohydrate-Protein Linkage Region of Proteglycans

已有证据表明，硫酸化的糖胺多聚糖具有多种生物活性。然而，它们的结构和生物合成机制还不完全清楚。在这项研究中，我们对包括软骨素、6-硫酸和肝素在内的各种硫酸糖胺聚糖的碳水化合物-蛋白质连接区进行了结构研究。虽然前者是半乳糖胺多聚糖，后者是氨基葡萄糖多聚糖，但它们在碳水化合物-蛋白质连接区具有共同的四糖核心结构。我们在鲨鱼软骨制备的软骨素6-硫酸酯的碳水化合物-蛋白质连接区发现了迄今未见报道的4-0-硫酸化和6-0-硫酸化半乳糖结构。这些结构是Galbeta1-3Gal(6-0-硫酸盐)Beta1-4Xyl，Gal(6-0-sulfate)beta1-3Gal(6-0-sulfate)beta1-4Xyl和Gal(4-0-sulfate)beta1-3Gal(6-0-sulfate)beta1-4Xyl.相反，在从猪…中制备的肝素的相应区域中没有检测到这些结构更多的时间。因此，本研究阐明了硫酸软骨素和肝素的碳水化合物-蛋白质连接区存在结构差异。基于这些结果，我们提出了一个可行的假设，即连接区域的半乳糖残基的硫酸盐化可能参与了硫酸软骨素和肝素的生物合成分选机制。将第一个GalNAc残基转移到连接四糖GlcAbeta1-3Galbeta1-3Galbeta1-4xyl的GalNAc转移酶可能识别硫酸盐化的半乳糖结构，而将第一个GlcNAc残基转移到连接四糖的GlcNAc转移酶则受到这些修饰结构的抑制。这项研究还揭示了基于碳水化合物蛋白连接区的结构差异，硫酸软骨素链中存在许多亚类。在未来的研究中，我们计划研究连接区和生物活性结构域所在的重复区域之间的结构关系。较少

It has become evident that the sulfated glycosaminoglycans exert various biological activities. However, their structure and biosynthetic mechanisms are not fully understood. In this study we carried out structural studies on the carbohydrate-protein linkage region of various sulfated glycosaminoglycans including chondroitin 6-sulfate ad heparin. Although the former is galactosaminoglycans and the latter is glucosaminoglycans, they share the common tetrasaccharide core structure in the carbohydrate-protein linkage region.We discovered hitherto unreported 4-0-sulfated and 6-0-sulfated galactose-containing structures in the carbohydrate-protein linkage region of chondroitin 6-sulfate prepared from shark cartilage. These strucures were Galbeta1-3Gal(6-0-sulfate)beta1-4Xyl, Gal(6-0-sulfate)beta1-3Gal(6-0-sulfate)beta1-4Xyl and Gal(4-0-sulfate)beta1-3Gal(6-0-sulfate)beta1-4Xyl. In contrast, these structures were not detected in the corresponding region of heparin prepared from porcine intes … More tine. Thus, this study has clarified that there are structural differences in the carbohydrate-protein linkage region of chondroitin sulfate and heparin. Based upon these results, we propose a working hypothesis that the sulfation of the galactose residues in the linkage region may be involved in the biosynthetic sorting mechanisms of chondroitin sulfate and heparin. It is possible that tha GalNAc-transferase which transfers the first GalNAc residue to the linkage tetrasaccharide, GlcAbeta1-3Galbeta1-3Galbeta1-4Xyl, recognaizes the sulfated galactose structures while the GlcNAc-transferase which transfers the first GlcNAc residue to the linkage tetrasaccharide is inhibited by these modified structures. This study also revealed that there are a number of subclasses in the chondroitin sulfate chains based upon the structural differences in the carbohydrate protein linkage region. In the future study we plan to investigate the structural relationship between the linkage region and the repeat region where biologically active domain structures are located. Less