Hospital Universitário Clementino Fraga Filho, Brazil.
Glycobiology. 2010 Jun;20(6):702-9. doi: 10.1093/glycob/cwq017. Epub 2010 Feb 10.
The sea urchin eggs are surrounded by a jelly coat, which contains sulfated polysaccharides with unique structures. These molecules are responsible for inducing the species-specific acrosome reaction, an obligatory event for the binding of sperm and fusion with the egg. The mechanism of biosynthesis of these sulfated polysaccharides is virtually unknown. The egg jelly of the sea urchin Echinometra lucunter contains a simple 2-sulfated, 3-linked alpha-L-galactan. Here, we pulse labeled the sea urchin ovary in vitro with (35)S-sulfate to follow the biosynthesis of the sulfated alpha-L-galactan. We found that the ovary contains a 2,6-disulfated, 3-linked alpha-L-galactan, which incorporates (35)S-sulfate more avidly than the 2-sulfated isoform. The 2,6-disulfated alpha-L-galactan was purified by anion exchange chromatography, analyzed by electrophoresis and characterized by 1D and 2D nuclear magnetic resonance spectra. We also investigated the location of the sulfated polysaccharides on the oocytes using histochemical procedures. The stain revealed high amounts of sulfated polysaccharide in mature oocytes and accessory cells. The amount of intracellular sulfated polysaccharides decreased as oocytes are spawned. We speculate that 2,6-disulfated galactan is initially synthesized in the ovary and that 6-sulfate ester is removed when the polysaccharide is secreted into the egg jelly. Similar events related to remodeling of sulfated polysaccharides have been reported in other biological systems.
海胆卵被一层胶状物质所包围，其中含有具有独特结构的硫酸多糖。这些分子负责诱导种特异性顶体反应，这是精子结合和与卵子融合的必要事件。这些硫酸多糖的生物合成机制实际上是未知的。海胆 Echinometra lucunter 的卵胶中含有一种简单的 2-硫酸化、3-连接的α-L-半乳糖聚糖。在这里，我们用（35）S-硫酸盐脉冲标记体外培养的海胆卵巢，以追踪硫酸化α-L-半乳糖聚糖的生物合成。我们发现卵巢中含有一种 2,6-二硫酸化、3-连接的α-L-半乳糖聚糖，它比 2-硫酸化异构体更能有效地掺入（35）S-硫酸盐。通过阴离子交换色谱法纯化 2,6-二硫酸化α-L-半乳糖聚糖，通过电泳进行分析，并通过 1D 和 2D 核磁共振谱进行表征。我们还使用组织化学程序研究了硫酸多糖在卵母细胞上的位置。染色显示成熟卵母细胞和附属细胞中含有大量的硫酸多糖。随着卵母细胞的排出，细胞内硫酸多糖的含量减少。我们推测 2,6-二硫酸化半乳糖聚糖最初在卵巢中合成，当多糖分泌到卵胶中时，6-硫酸酯被去除。在其他生物系统中，也有报道了与硫酸多糖重塑相关的类似事件。
