Regulation of glycolipid expression and its disorder

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Isolation and characterization of sialyltransferases which synthesize bioactive gangliosides were carried out.[1] High sensitive and non-radioactive assay method for sialyltransferases: To improve the assay method of ganglioside sialyltransferase activity, we used pryridylamine-labeled oligosaccharides as substrate.These fluorescent substrates were well separated in HPLC and were applicable in sialyltransferase assay. Ganglioside was digested by endoglycoceramidase and released oligosaccharide was labeled by pyridylamine. Sialyltransferase was partially purified from membrane fraction of rat liver Golgi apparatus. Pyridylamine labelled GM3-oligosaccharide was good substrate for GD3 synthase as native GM3 gangliosede. But, Pyridylamine labelled oligosaccharide of CDH was poor substrate for GM3 synthase. Detergent requirment for full activity of GD3 synthase was reduced suggesting that detergent act in part not only as solubilizer of enzyme but also raise availability of glycolipids[2] P … More hoto-affinity labeling of sialyltransferase: Photoactive diazilin derivatives of lactosylceramide and CMP-NeuAc which were the substrate of sialyltransferase (GM3 synthase). These compounds were good substrates and had high affinity to GM3 synthase, respectively. Some molecules were specifically labeled by these compounds and detected by SDS-PAGE autoradiography.[3] Characterization and biosynthesis of gangliosides in developing Xenopus laevis: Change of ganglioside species during early development of Xenopus laevis were studied. Major ganglioside in oocyte was GalNAc-GM1b. There is two possible pathways for in vivo synthesis of GalNAc-GM1b. UDP-GalNAc : GM1b beta1-3 N-acetylgalactosaminyl transferase activity was only detected in Xenopus membrane fraction. These suggest that GalNAc-GM1b was synthesized via GM1b from gangliotetraosylceramide in Xenopus. Dramatical elevation of level of GalNAc-GM1b and GM3 was observed after fertilization. Several lines of evidence suggest that alpha2-3 sialyltransferase activity was elevated during this stage. Less