Composition and synthesis of three higher ganglioside homologs in bovine mammary tissue

Three higher gangliosides were identified as constituents of bovine mammary gland. The structures of these three gangliosides were shown to be ceramide-glucose-galactose-(sialic acid)-N-acetylgalactosamine-galactose, ceramide-glucose-galactose-(sialic acid)₂-N-acetylgalactosamine, and ceramide-glucose-galactose-(sialic acid)₂-N-acetylgalactosamine-galactose These gangliosides accounted for only a small fraction (<20%) of the lipid-bound sialic acid in mammary gland. While fatty acids with even carbon numbers from C₁₄ to C₂₆ were predominant in these gangliosides, they also contained C₂₃ and C₂₅ fatty acids. Mammary gland Golgi apparatus-rich fractions had all glycosyltransferases required for synthesis of these gangliosides starting with ceramide.