Glycosphingolipid Biosynthesis through Asialogangliosides in Rat Bone Marrow Cells

Abstract

Glycolipid biosynthesis in rat bone marrow cells has been studied with reference to four kinds of glycosyltransferases catalyzing the transfer of N-acetylgalactosamine, galactose, N-acetylneuraminic acid, and fucose to each glycolipid acceptor. It was demonstrated that glycosyltransferase activities which synthesize galactosylglucosylceramide (CDH) from glucosylceramide (CMH), N-acetylgalactosaminylgalactosylglucosylceramide (GA₂) from CDH, galactosyl-N-acetylgalactosaminylgalactosylglucosylceramide (GA₁) from GA₂ and N-acetylneuraminylgalactosyl-N-acetylgalactosaminylgalactosylglucosylceramide (GM_1b) from GA₁ were all present in rat bone marrow cell homogenate. Fucosyltransferase activity catalyzing the transfer of fucose from GDP-fucose to GA₁ was also recognized in the cell homogenate. Neutral glycolipid extracted from rat bone marrow cells was analyzed by thin layer chromatography and glycosidase treatments. The presence of glycolipids corresponding to GA₂, GA₁, and fucolipid was demonstrated. From these results, it was concluded that the biosynthesis of glycolipid through asialogangliosides is a major biosynthetic route in rat bone marrow cells.