出版社：American Society for Biochemistry and Molecular Biology
摘要：The galactose oxidase–sodium borohydride method was used to specifically label the terminal N -acetylgalactosamine of three glycosphingolipids, G m 2-ganglioside, asialo-G m 2-ganglioside, and globoside. All of the compounds showed a minimum of 95% radiopurity, and generally more than 90% of the total radioactivity was located in the terminal galactosamine moiety. Globoside and asialo-G m 2-ganglioside were labeled to high specific activities comparable with those of the sphingolipids with a terminal galactose moiety, labeled with the same procedure. These labeled compounds were well suited as substrates for the study of specific sphingolipid N -acetylgalactosaminidase. G m 2-ganglioside, however, was a poor substrate for galactose oxidase, and its specific activity was only a small percentage of the others. Furthermore, because of the low specific activity of the galactosamine moiety, it was necessary to pretreat G m 2-ganglioside with unlabeled sodium borohydride to reduce the nonspecific labeling of other portions of the molecule. The use of labeled sodium borohydride of a very high specific activity may yield specifically labeled G m 2-ganglioside suitable for metabolic studies. Thus, the method is useful for labeling not only terminal galactose but also terminal N -acetylgalactosamine of glycosphingolipids.
关键词：G m 2-ganglioside ; asialo-G m 2-ganglioside ; globoside
