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Lactonization of GD1b ganglioside under acidic conditions.
Gangliosides that contain the disialosyl residue alpha-Neu5Ac-(2--8)-alpha-Neu5Ac-(2--3)- can lactonize in the presence of traces of acid and this reaction has been studied in detail on GD1b [beta-Gal-(1--3)-beta-GalNAc-(1 --4)-[alpha-Neu5Ac-(2--8)-alpha-Neu5Ac-(2 --3)]-beta-Gal-(1--4)-beta-Glc-1--1)-Cer]. Lactonization occurs rapidly at a proton-ganglioside molar ratio of less than 1. At equilibrium, the ratio of GD1b to its lactone is 3:7. The data suggest the possibility that a proton-driven lactonization of gangliosides may occur in vivo.
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