Cheng F, Heinegård D, Malmström A, Schmidtchen A, Yoshida K, Fransson L A
Department of Medical and Physiological Chemistry, Lund University, Sweden.
Glycobiology. 1994 Oct;4(5):685-96. doi: 10.1093/glycob/4.5.685.
Dermatan sulphate is a co-polymer of two types of disaccharide repeats: D-glucuronate-N-acetylgalactosamine and L-iduronate-N-acetylgalactosamine. The former can be O-sulphated at C-4 or C-6 of the galactosamine, whereas the latter contains almost exclusively 4-O-sulphated galactosamine. A minor proportion of the L-iduronate may be O-sulphated at C-2. Chondroitin sulphate has no L-iduronate-containing repeats. We have used our recently developed methods for sequence analysis of galactosaminoglycans to investigate the structure of dermatan/chondroitin sulphates of the proteoglycans decorin and biglycan derived from various bovine tissues, like dermis, sclera, tendon, aorta, cartilage and bone. The glycan chains, radioiodinated at the reducing end, were partially cleaved with specific enzymes (chondroitin lyases), and subjected to high-resolution polyacrylamide gel electrophoresis, blotting and autoradiography to identify fragments extending from the labelled reducing end to the point of cleavage. We used chondroitin B lyase to identify the location of L-iduronate, chondroitin AC-I lyase to locate D-glucuronate and chondroitin C lyase to cleave where D-glucuronate residues were succeeded by 6-O-sulphated N-acetylgalactosamine. We could demonstrate tissue-specific, periodic and wave-like patterns of distribution for the two epimeric uronic acids, as well as specific patterns of sulphation in dermatan sulphates derived from either decorin or biglycan. For example, some dermatan sulphates contained D-glucuronate-rich domains that were always 6-sulphated (scleral decorin), others were always 4-sulphated (decorin from bovine dermis, cartilage and bone; biglycan from aorta) or 6-sulphated near the linkage region, but 4-sulphated in more distal domains (decorin from porcine dermis and bovine tendon). Decorin from bone and articular cartilage, as well as biglycan from articular and nasal cartilage, carried largely chondroitin sulphate chains, but also some dermatan sulphate, whereas galactosaminoglycan chains derived from aggrecan of nasal cartilage were free of L-iduronate. Decorin and biglycan from the same tissue (articular cartilage or sclera) had similar glycan chains. The two side chains in a biglycan molecule are probably also similar to one another. The portion of the glycan chains nearest to the core protein was substituted with charged groups to a variable degree, which may correlate with the structural features of the main chain.
D-葡糖醛酸-N-乙酰半乳糖胺和L-艾杜糖醛酸-N-乙酰半乳糖胺。前者的半乳糖胺在C-4或C-6位可被O-硫酸化,而后者几乎只含有4-O-硫酸化的半乳糖胺。一小部分L-艾杜糖醛酸可能在C-2位被O-硫酸化。硫酸软骨素没有含L-艾杜糖醛酸的重复单元。我们运用最近开发的用于分析氨基半乳糖聚糖序列的方法,研究了源自各种牛组织(如真皮、巩膜、肌腱、主动脉、软骨和骨骼)的核心蛋白聚糖和双糖链蛋白聚糖的硫酸皮肤素/硫酸软骨素的结构。在还原端进行放射性碘化的聚糖链,用特定酶(软骨素裂解酶)进行部分切割,然后进行高分辨率聚丙烯酰胺凝胶电泳、印迹和放射自显影,以鉴定从标记的还原端延伸至切割点的片段。我们用硫酸软骨素B裂解酶确定L-艾杜糖醛酸的位置,用硫酸软骨素AC-I裂解酶确定D-葡糖醛酸的位置,用硫酸软骨素C裂解酶在D-葡糖醛酸残基后接6-O-硫酸化的N-乙酰半乳糖胺处进行切割。我们能够证明两种差向异构糖醛酸的组织特异性、周期性和波浪状分布模式,以及源自核心蛋白聚糖或双糖链蛋白聚糖的硫酸皮肤素中的特定硫酸化模式。例如,一些硫酸皮肤素含有富含D-葡糖醛酸的结构域,这些结构域总是6-硫酸化的(巩膜核心蛋白聚糖),另一些总是4-硫酸化的(牛真皮、软骨和骨骼中的核心蛋白聚糖;主动脉中的双糖链蛋白聚糖),或者在连接区域附近是6-硫酸化的,但在更远端的结构域是4-硫酸化的(猪真皮和牛肌腱中的核心蛋白聚糖)。来自骨骼和关节软骨的核心蛋白聚糖,以及来自关节和鼻软骨的双糖链蛋白聚糖,主要携带硫酸软骨素链,但也有一些硫酸皮肤素,而源自鼻软骨聚集蛋白聚糖的氨基半乳糖聚糖链不含L-艾杜糖醛酸。来自同一组织(关节软骨或巩膜)的核心蛋白聚糖和双糖链蛋白聚糖具有相似的聚糖链。双糖链蛋白聚糖分子中的两条侧链可能彼此也相似。聚糖链中最靠近核心蛋白的部分被不同程度地带有电荷的基团取代,这可能与主链的结构特征相关。