A sialyltransferase activity which catalyzes the synthesis of sialosylgalactosylceramide (G7) from added galactocerebroside and CMP N acetylneuraminic acid has been demonstrated in mouse brain microsomes. The enzyme reactions shows a pH optimum of 6.3 and requires detergents. Both Mn2+ and Ca2+ inhibited the reaction, whereas Mg2+ had no effect. The apparent Km for galactocerebroside leading to G7 was estimated to be 8.7 x 10-4 M. The same microsomal preparation also synthesized hematoside when ceramide lactoside was the glycolipid acceptor. The apparent Km for ceramide lactoside was about 1/10th that for galactocerebroside. When the preparations were partially inactivated by heat the synthesis of G7 and of hematoside was reduced at approximately the same rate. Liver appeared to have the highest activity for G7 synthesis (as well as of hematoside), followed by brain. The synthesis of G7 by mouse brain microsomes in vitro demonstrates a new pathway for brain ganglioside synthesis.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of Biological Chemistry|
|State||Published - Dec 1 1976|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology