Isolation and characterization of a novel phytosphingosine-containing G(M2) ganglioside from mullet roe (Mugil cephalus)

The major ganglioside from the roe of striped mullet (Mugil cephalus) has been isolated and purified. Compositional analysis of this ganglioside revealed that it contained and equimolar ratio of the following residues: N-acetylneuraminic acid, N-acetylgalactosamine, galactose, glucose, and the long-chain base. Further structural studies by sequential enzymatic hydrolysis, permethylation analysis, and proton NMR spectroscopy indicated that the structure of the oligosaccharide moiety was identical to that of G(M2) ganglioside from human brain: GalNAcβ1→4Galβ1→4(3←2αNeuAc)-Glc→ceramide. This ganglioside, however, differed from brain G(M2) in its ceramide portion. The most striking differences are the presence of large amounts of C₁₈ and C₂₀ phytosphingosine (over 80% of the total long-chain bases) and the preponderance of monounsaturated α-hydroxy fatty acids (over 80%). Such a phytosphingosine-containing G(M2) ganglioside has never been reported.