JBC, Vol. 250, Issue 17, 6727-6734, Sep, 1975
Sialic acids. Enzymatic synthesis of Tay-Sachs ganglioside
J. C. Steigerwald, S. Basu, B. Kaufman and S. Roseman
A particulate preparation from embryonic chicken brain catalyzed the
transfer of N-acetylgalactosamine from uridine
diphospho-N-acetylgalactosamine to the ganglioside GM3 (hematoside,
sialyllactosylceramide). The kinetic properties of the transferase were
determined. The product was isolated and on the basis of chemical analysis
and chromatographic behavior was shown to be Tay-Sachs ganglioside (GM2).
The particulate preparation also utilized N-acetyl-D-glucosamine and some
of its derivatives as acceptors, but partial heat inactivation and
substrate competition experiments indicated that the two classes of
acceptors, hematoside and N-acetylglucosamine, were substrates for
different N-acetylgalactosaminyltransferases. The enzyme that utilized
hematoside showed low but detectable activity with analogues such as
lactosylceramide and sialyllactose, but no activity with a wide range of
other beta-galactosides and glycosphingolipids. These results are in accord
with a proposed pathway for the biosynthesis of the gangliosides and for
the patterns of these substances in different cell types and tissues.