Unique catabolic pathway of Glycosphingolipids in a hydrozoan, Hydra magnipapillata, involving endoglycoceramidase
Unique catabolic pathway of Glycosphingolipids in a hydrozoan, Hydra magnipapillata, involving endoglycoceramidase
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DOI：
10.1074/jbc.m401460200
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发表时间：
2004-08-06
影响因子：
4.8
通讯作者：
Ito, M
中科院分区：
文献类型：
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作者：
Horibata, Y;Sakaguchi, K;Ito, M
神经酰胺内切酶(EGCase；EC 3.2.1.123)是一种能够切断各种神经鞘糖脂的寡糖和神经酰胺之间的糖苷键的酶。我们在线虫、软体动物和环节动物中检测到了较强的EGCase活性，并从九头蛇中克隆了该酶。该酶由517个氨基酸残基组成，与红球菌和水母EGCase的同源性分别为19.2%和50.2%。在CHOP(中国仓鼠卵巢细胞表达多发性瘤LT抗原)细胞中表达的重组水合酶能降解[C-14]GM1a生成[C-14]神经酰胺，其最适pH为3.0-3.5。整装原位杂交和免疫细胞化学分析表明，EGCase广泛表达于内胚层，尤其是消化细胞。注射入胃腔的GM1a被EGCase直接降解生成GM1a寡糖和神经酰胺，分别被外切糖苷酶和神经酰胺酶进一步降解。然而，水合胞外糖苷酶并不直接水解GM1a。这些结果表明，EGCase在水产动物饲料中鞘糖脂的分解过程中是必不可少的，这表明了动物体内唯一的鞘糖脂分解代谢途径。
Endoglycoceramidase (EGCase; EC 3.2.1.123) is an enzyme capable of cleaving the glycosidic linkage between oligosaccharides and ceramides of various glycosphingolipids. We detected strong EGCase activity in animals belonging to Cnidaria, Mollusca, and Annelida and cloned the enzyme from a hydra, Hydra magnipapillata. The hydra EGCase, consisting of 517 amino acid residues, showed 19.2% and 50.2% identity to the Rhodococcus and jellyfish EGCases, respectively. The recombinant hydra enzyme, expressed in CHOP ( Chinese hamster ovary cells expressing polyoma LT antigen) cells, hydrolyzed [C-14] GM1a to produce [C-14] ceramide with a pH optimum at 3.0 - 3.5. Whole mount in situ hybridization and immunocytochemical analysis revealed that EGCase was widely expressed in the endodermal layer, especially in digestive cells. GM1a injected into the gastric cavity was incorporated and then directly catabolized by EGCase to produce GM1a-oligosaccharide and ceramide, which were further degraded by exoglycosidases and ceramidase, respectively. However, hydra exoglycosidases did not hydrolyze GM1a directly. These results indicate that the EGCase is indispensable for the catabolic processing of dietary glycosphingolipids in hydra, demonstrating the unique catabolic pathway for glycosphingolipids in the animal.