Isolation and Cell Biological Characterization of Sialyltransferases Involved in Ganglioside Biosynthesis

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To elucidate the role of sugar chain of ganglioside in cell recognition and signal transduction, isolation and characterization of sialyltransferases which synthesize bioactive gangliosides, was investigated.[1]Solubilization of membrane-bound sialyltransferase from rat liver Golgi apparatus using novel cationic detergent : For effective identification of sialyltransferase, novel cationic detergent, sodium polyoxyethylenelaulylethersulfate/ laulyldimethylamineoxide mixture (7 : 3) was used for solubilization of the enzyme. One of the sialyltransferase, GD3 synthase(alpha2-8 sialyltransferase) succeeded in solubilization as active form. This detergent was also useful for evaluation of molecular weight and subunit structure by polyacrylamide gel electrophoresis.[2]Photo-affinity labelling of sialyltransferases : Photoactive di-azilin derivatives of lactosylceramide which was the substrate of GM3 synthase, was synthesized. This compound was well-substrate and had high affinity to GM3 synthase from rat liver Golgi apparatus. This compound had biotin-residue in molecule and could be utilized for identification and isolation of the labelled sialyltransferases.[3]Structural characterization of gangliosides in Xenopus laevis oocyte : To evaluate Xenopus oocyte as the host cells for the expression of foreign gene involved in the expression of sugar chain such as glycosyltransferases, glycosphigolipids of Xenopus oocyte were analyzed. From the results of sugar composition analysis, enzymatic hydrolysis, pennethylation analysis, and negative ion fast atom bombardment mass spectrometry, the structure of one of the major ganglioside was determined to be as follows :