Biochemical Properties of N-Methylamides of Sialic Acids in Gangliosides

抄録

A simple and rapid method for the preparation of N-methylamides (-CONHCH₃) of sialic acids in gangliosides and biochemical properties of the modified gangliosides are described. The sialic acid carboxyl groups of gangliosides were esterified with CH₃I-dimethylsulfoxide, followed by heating with monomethylamine. The modified gangliosides were chemically identified by TLC, IR spectroscopy, GLC-mass spectrometry and NMR spectroscopy.
The N-methylamide derivative of G_M1 produced a high titer IgG antibody. The antibody weakly cross-reacted with the methylester of G_M1 and its reductive derivative but did not react with the intact G_M1.
A monoclonal antibody (M2590) specific for G_M3 did not react with carboxyl-modified G_M3 (methylester, N-methylamide, and reduced G_M3), but it reacted with modified G_M3 which contains the C₇-analog of the sialic acid.
Clostridium perfringens and Arthrobacter ureafaciens sialidases did not hydrolyze the N-methylamide derivatives, methylesters or reductive derivatives of the ganglio-sides and, furthermore, these derivatives did not inhibit the actions of these sialidases.