Ishibashi Yohei, Kiyohara Masashi, Okino Nozomu, Ito Makoto
Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
J Biochem. 2007 Aug;142(2):239-46. doi: 10.1093/jb/mvm125. Epub 2007 Jun 13.
Endoglycoceramidase is a glycohydrolase capable of hydrolysing the O-glycosidic linkage between oligosaccharides and ceramides of various glycosphingolipids. However, no endoglycoceramidase reported so far can hydrolyse 6-gala series glycosphingolipids which possess the common structure R-Gal beta1-6Gal beta1-1'Cer. Recently, we found a novel endoglycoceramidase (endogalactosylceramidase, EGALC) which specifically hydrolyses 6-gala series glycosphingolipids. Here, we report that EGALC catalyses the hydrolysis as well as transglycosylation. An intact sugar chain of neogalatriaosylceramide (Gal beta1-6Gal beta1-6Gal beta1-1'Cer) was found to be transferred by EGALC to a primary hydroxyl group of various alkanols and non-ionic detergents such as Triton X-100 generating corresponding alkyl- and Triton-trigalactooligosaccharides. Furthermore, fluorescent 6-gala series glycosphingolipids were synthesized by transglycosylation in a reaction with EGALC using fluorescent ceramides as acceptors. Because of high efficiency and broad acceptor specificity, EGALC would facilitate the synthesis of fluorescent glycosphingolipids and neoglycoconjugates which contain 6-gala oligosaccharides.
内糖神经酰胺酶是一种糖水解酶，能够水解各种糖鞘脂的寡糖与神经酰胺之间的O-糖苷键。然而，迄今为止报道的内糖神经酰胺酶均无法水解具有共同结构R-Galβ1-6Galβ1-1'Cer的6-半乳糖系列糖鞘脂。最近，我们发现了一种新型的内糖神经酰胺酶（内半乳糖基神经酰胺酶，EGALC），它能特异性水解6-半乳糖系列糖鞘脂。在此，我们报道EGALC既能催化水解反应，也能催化转糖基化反应。新乳糖神经酰胺（Galβ1-6Galβ1-6Galβ1-1'Cer）完整的糖链被EGALC转移至各种链烷醇和非离子去污剂（如Triton X-100）的伯羟基上，生成相应的烷基-和Triton-三半乳糖寡糖。此外，在与EGALC的反应中，以荧光神经酰胺作为受体，通过转糖基化反应合成了荧光6-半乳糖系列糖鞘脂。由于效率高且受体特异性广，EGALC将有助于合成含有6-半乳糖寡糖的荧光糖鞘脂和新糖缀合物。
