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A unique biosynthetic pathway for gangliosides exists in Xenopus laevis oocytes
1Department of Biochemical Cell Research, Tokyo Metropolitan Institute of Medical Science, Japan.
Abstract:
It was previously reported that monosialosylgangliopentaosyl ceramide (GalNAc-GM1b) was a major ganglioside in Xenopus laevis oocytes. Here we determined biosynthetic pathways for the ganglioside by detailed measurements of glycosyltransferase activities. CMP-NeuAc:asialo-GM1 alpha 2-3 sialyltransferase (alpha 2-3 ST) and UDP-GalNAc:GM1b beta 1-4 N-acetylgalactosaminyltransferase (beta 1-4 GalNAcT) exhibited much higher activity than CMP-NeuAc:GalNAc-GA1 alpha 2-3 ST and UDP-GalNAc:asialo-GM1 beta 1-4 GalNAcT, respectively. These observations indicated the existence of a unique biosynthetic pathway in the oocytes as follows; asialo-GM1-->GM1b-->GalNAc-GM1b.