Oegema T R, Kraft E L, Jourdian G W, Van Valen T R
J Biol Chem. 1984 Feb 10;259(3):1720-6.
Proteoglycans isolated from the Swarm rat chondrosarcoma were shown to contain 35 mol of phosphate/mol of proteoglycan. While 20% of this phosphate was released by digestion with dilute alkali in the presence of sodium borohydride and is presumably of the phosphoserine/phosphothreonine type, 78% of the phosphate copurified with the peptide-free chondroitin sulfate chains. When chondroitin sulfate chains purified by ethanol precipitation or Sephacryl S200 column chromatography were digested with chondroitinase AC and the digests chromatographed on Bio-Gel P-4, the phosphate co-migrated with a carbohydrate fragment that contained 2 glucuronic acid (one as delta 4,5-unsaturated sugar), 1-galactosamine, 2-galactose, and 1-phosphate residue/xylitol. A second fragment of similar composition but lacking phosphate was also recovered in a ratio of about 3 to 1 relative to the phosphorylated fragment. The phosphate in the chondroitin sulfate linkage region fragment had the alkaline phosphatase sensitivity as well as 31P NMR spectra of a monophosphate esterified to a secondary sugar alcohol. The phosphate was localized on the C-2 of the chain initiating xylose since these residues as xylitol showed a delayed release during acid hydrolysis and the xylitol was recovered intact after periodate oxidation. In the chondrosarcoma, 2-phosphoxylose appears to be a normal synthetic product since [32P]phosphate was readily incorporated into the proteoglycan and the incorporated isotope had similar biochemical properties as the unlabeled phosphate.
从群体大鼠软骨肉瘤中分离出的蛋白聚糖显示，每摩尔蛋白聚糖含有35摩尔磷酸盐。其中20%的磷酸盐在硼氢化钠存在下用稀碱消化可释放出来，推测为磷酸丝氨酸/磷酸苏氨酸类型，而78%的磷酸盐与无肽硫酸软骨素链共纯化。当通过乙醇沉淀或Sephacryl S200柱色谱纯化的硫酸软骨素链用软骨素酶AC消化，消化产物在Bio-Gel P-4上进行色谱分析时，磷酸盐与一个碳水化合物片段共迁移，该片段含有2个葡萄糖醛酸（一个为δ4,5-不饱和糖）、1个半乳糖胺、2个半乳糖和1个磷酸残基/木糖醇。还回收了一个组成相似但不含磷酸盐的第二个片段，其与磷酸化片段的比例约为3比1。硫酸软骨素连接区片段中的磷酸盐具有碱性磷酸酶敏感性以及单磷酸酯与仲糖醇酯化的31P NMR光谱。磷酸盐位于链起始木糖的C-2位，因为这些残基作为木糖醇在酸水解过程中显示出延迟释放，并且在高碘酸盐氧化后木糖醇完整回收。在软骨肉瘤中，2-磷酸木糖似乎是一种正常的合成产物，因为[32P]磷酸盐很容易掺入蛋白聚糖中，并且掺入的同位素具有与未标记磷酸盐相似的生化特性。
