Pavão M S, Rodrigues M A, Mourão P A
Departamento de Bioquímica, Universidade Federal do Rio de Janeiro, Brazil.
Biochim Biophys Acta. 1994 Apr 21;1199(3):229-37. doi: 10.1016/0304-4165(94)90001-9.
Histochemical and chemical analyses reveal important differences between tunic and body of the ascidian Styela plicata. The body contains hydroxyproline, nucleic acid and hexuronic acid. Analyses of the hexuronic acid-containing molecules indicates the presence of dermatan sulfate and heparan sulfate. The tunic, on the other hand, contains no hydroxyproline and small amounts of nucleic acid and hexuronic acid. Large amounts of sulfated polysaccharides, identified by agarose gel electrophoresis, are also present in the tunic. In vitro, incorporation of 35S-sulfate and 14C-glucose and 35S-sulfate pulse-chase experiments show that sulfate and glucose are incorporated into the sulfated polysaccharides of the tunic. The radioactivity is associated mainly with the region of the tunic containing the epidermal cells; however, a small amount of radioactivity is also detected in other regions of the tunic, suggesting that the sulfated polysaccharides are synthesized mainly by the epidermal cells and, to a small extent, by other cell types present in the tunic. Conversion of D-glucose to L-galactose, previously observed in the tunic of Styela plicata (Biochemistry 30, 3458-3464, 1990) is more intense in the region of the tunic containing the epidermal cells.
组织化学和化学分析揭示了皱瘤海鞘被囊和身体之间的重要差异。身体含有羟脯氨酸、核酸和己糖醛酸。对含己糖醛酸分子的分析表明存在硫酸皮肤素和硫酸乙酰肝素。另一方面，被囊不含羟脯氨酸，含有少量核酸和己糖醛酸。通过琼脂糖凝胶电泳鉴定，被囊中还存在大量硫酸化多糖。在体外，35S-硫酸盐和14C-葡萄糖的掺入以及35S-硫酸盐脉冲追踪实验表明，硫酸盐和葡萄糖被掺入到被囊的硫酸化多糖中。放射性主要与被囊中含有表皮细胞的区域相关；然而，在被囊的其他区域也检测到少量放射性，这表明硫酸化多糖主要由表皮细胞合成，在一定程度上也由被囊中存在的其他细胞类型合成。在皱瘤海鞘被囊中先前观察到的D-葡萄糖向L-半乳糖的转化（《生物化学》30，3458 - 3464，1990）在被囊中含有表皮细胞的区域更为强烈。
