Chemical structure of monosialoganglioside GM1b biosynthesized in vitro.

The structure of a neuraminidase-labile monosialoganglioside which is formed in vivo from asialoganglioside (galactosyl (beta, 1 in equilibrium 3) N-acetylgalactosaminyl (beta, 1 in equilibrium 4) galactosyl (beta, 1 in equilibrium 4) glucosyl (1 in equilibrium 1) ceramide) and cytidine-5'-monophospho-N-acetylneuraminic acid in the presence of young rat brain sialytransferase has been established. This monosialoganglioside contains a neuraminidase-labile N-acetylneuraminyl group which is linked at position C-3 of the terminal galactosyl unit. This result was obtained by ultramicro scale permethylation of radioactive neuraminidase-labile monosialoganglioside biosynthesized from asialoganglioside labeled with tritium in the terminal galactose.