Composition and Synthesis of Gangliosides in Bovine Testis, Sperm and Seminal Plasma

Abstract

Gangliosides were identified as constituents of bovine testis, sperm and seminal plasma. Based on sialic acid content, the average concentrations of gangliosides in bovine testis, sperm and seminal plasma were 1.6, 2.25 and 0.30 nmoles/mg protein. Seven chromatographically distinguishable gangliosides were found. The structures of five testicular gangliosides were shown to be N-acetylneuraminylgalactosylglucosyl ceramide (GM₃)¹ ; N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosyglucosyl ceramide (GM₂); (N-acetylneuraminyl)₂-galactosylglucosyl ceramide (GD₃); galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosyl ceramide (GM₁ ); and N-acetylneuraminyl-galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosyl ceramide (GD_1a). The structure of the major ganglioside constituent of bovine sperm was shown to be identical to GM₃. Saturated fatty acids of even carbon numbers from C₁₄ to C₂₄ were found in gangliosides. Appreciable amounts of n-uncosanoic (C₂₁) and n-tricosanoic (C₂₃) acids were also present. Testis tissue contained the galactosyl- and sialyltransferases for the synthesis of N-acetylneuraminyl-galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosyl ceramide (GD_1a) starting from glucosyl ceramide.