Heaney-Kieras J, Rodén L, Chapman D J
Biochem J. 1977 Jul 1;165(1):1-9. doi: 10.1042/bj1650001.
The extracellular anionic polysaccharide isolated from cultures of a unicellular red alga, Porphyridium cruentum, contains a small amount of protein after extensive purification. The polysaccharide and protein are recovered in the same fraction after isopycnic CsCl-density-gradient centrifugation in 4M-guanidinium chloride, under conditions designed to separate proteins from polysaccharide. The peptide portion of the protein-polysaccharide is released from the polysaccharide by alkali under conditions for beta-elimination. The released peptide is non-diffusible, but in can be separated from the polysaccharide by precipitation of the polysaccharide as the cetylpyridinium complex. Under conditions for beta-elimination of certain O-glycosidic carbohydrate-protein linkages, selective destruction of serine and threonine occurs. The addition of a reducing agent to the alkali mixture produces a selective increase in alanine and alpha-aminobutyric acid. Addition of a tritiated reducing agent to the alkali mixture produces radioactive alanine and alpha-aminobutyric acid, and xylitol as the only sugar alcohol. Similar results are obtained from glycopeptides isolated from partial acid hydrolysates. A macromolecular structure of the protein-polysaccharide is suggested by a comparison of the intrinsic viscosity of material before and after treatment with alkali and proteolytic enzymes.
从单细胞红藻紫球藻（Porphyridium cruentum）培养物中分离得到的细胞外阴离子多糖，经过广泛纯化后仍含有少量蛋白质。在旨在将蛋白质与多糖分离的条件下，于4M氯化胍中进行等密度CsCl密度梯度离心后，多糖和蛋白质在同一组分中被回收。蛋白质 - 多糖的肽部分在β-消除条件下通过碱从多糖中释放出来。释放出的肽不可扩散，但可通过将多糖沉淀为十六烷基吡啶复合物而与多糖分离。在某些O-糖苷碳水化合物 - 蛋白质键的β-消除条件下，丝氨酸和苏氨酸会发生选择性破坏。向碱混合物中添加还原剂会使丙氨酸和α-氨基丁酸选择性增加。向碱混合物中添加氚标记的还原剂会产生放射性丙氨酸和α-氨基丁酸，以及木糖醇作为唯一的糖醇。从部分酸水解产物中分离得到的糖肽也得到了类似的结果。通过比较碱处理和蛋白酶处理前后材料的特性粘度，推测出蛋白质 - 多糖的大分子结构。
