Constant and variable domains of different disaccharide structure in corneal keratan sulphate chains.
Constant and variable domains of different disaccharide structure in corneal keratan sulphate chains.
复制标题
角膜硫酸角质素链中不同二糖结构的恒定和可变结构域。
作者：
M. Oeben;R. Keller;H. Stuhlsatz;H. Greiling
从猪角膜硫酸角蛋白的分布光谱中切下四个不同MR和硫化程度的肽基角蛋白硫酸盐组分。用角聚糖酶彻底消化后，用DEAE-Sephacel和Bio-Gel P-10分离，分析它们的MR、硫酸化度、氨基糖和中性糖含量。研究发现，每个糖胺多糖链都由一个恒定的非硫化和单硫化双糖单元结构域和一个可变域的二硫化二糖单元构成。从分离的连接区低聚糖中回收了四种肽角蛋白硫酸酯的总神经氨酸。在动力学研究中，研究了四种肽基角蛋白硫酸酯与角聚糖酶孵育不同时间后的MR分布。在任何降解时间都没有明显的中等大小的产物出现，而是不断地向较低的MR转变。在很短的孵育期后，连接区的寡糖就已经被释放了。从这些动力学研究的结果与神经氨酸分析的结果相结合，表明每个硫酸酯角蛋白分子只有一条二糖链。提出了一种角膜硫酸角蛋白的模型。连接区中的一个α-甘露糖残基与由乳糖胺和末端唾液酸组成的低聚糖结合。另一个α-甘露糖残基连接在二糖链上。这条链在还原末端含有一个或两个非硫化二糖单元，紧随其后的是10-12个单硫化二糖单元。可变长度的二硫化二糖部分位于链的非还原末端。
Four peptidokeratan sulphate fractions of different Mr and degree of sulphation were cut from the pig corneal keratan sulphate distribution spectrum. After exhaustive digestion with keratanase, the fragments were separated on DEAE-Sephacel and Bio-Gel P-10 and analysed for their Mr, degree of sulphation and amino sugar and neutral sugar content. It was found that every glycosaminoglycan chain is constructed of a constant domain of non-sulphated and monosulphated disaccharide units and a variable domain of disulphated disaccharide units. Total neuraminic acid of the four peptidokeratan sulphates was recovered from their isolated linkage-region oligosaccharides. In kinetic studies, the four peptidokeratan sulphates were investigated for Mr distribution after various incubation times with keratanase. There was a continuous shift towards lower Mr and no appearance of a distinct intermediate-sized product at any degradation time. The linkage-region oligosaccharide was already being liberated after a very short incubation period. From the results of these kinetic investigations in connection with the results of neuraminic acid analyses it is suggested that there exists only one disaccharide chain per peptidokeratan sulphate molecule. A model of corneal keratan sulphate is postulated. One of the alpha-mannose residues in the linkage region is bound to an oligosaccharide consisting of a lactosamine and a terminal sialic acid. The other alpha-mannose residue is attached to the disaccharide chain. This chain contains one or two non-sulphated disaccharide units at the reducing end, followed by 10-12 monosulphated disaccharide units. The disulphated disaccharide moiety of variable length is positioned at the non-reducing end of the chain.