LACTONIZATION OF GD1B GANGLIOSIDE UNDER ACIDIC CONDITIONS

Gangliosides that contain the disialosyl residue α-Neu5Ac-(2→8)-α-Neu5Ac-(2→3)- can lactonize in the presence of traces of acid and this reaction has been studied in detail on GD1b {β-Gal-(1→3)-β-GalNAc-(1→4)-[α-Neu5Ac-(2→8)-α-Neu5Ac-(2→3)]-β-Gal-(1→4)-β-Glc-(1→1)-Cer}. Lactonization occurs rapidly at a proton-ganglioside molar ratio of ≫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.