Complexing of Glycolipids and Their Transfer between Membranes by the Activator Protein for Degradation of Lysosomal Ganglioside G M2

The lysosomal degradation of ganglioside GMZ by hexosaminidase A depends on the presence of the specific activator protein which mediates the interaction between micellar or membrane‐bound ganglioside and water‐soluble hydrolase. The mechanism and the glycolipid specificity of this activator were studied in more detail.1 It could be shown with three different techniques (isoelectric focusing, centrifugation and electrophoresis) that the activator protein extracts glycolipid monomers from micelles or liposomes to give water‐soluble complexes with a stoichiometry of 1 mol of glycolipid/mol of activator protein. Liposome‐bound ganglioside G m2 is considerably more stable against extraction and degradation than micellar ganglioside. 2 In the absence of enzyme the activator acts in vitro as glycolipid transfer protein, transporting glycolipids from donor to acceptor membranes. 3 The activator protein is rathcr specific for ganglioside G M2 . Other glycolipids (G M3 , G M1 , G Dla and G A2 ) form less stable complexes with the activator and are transferred at a slower rate (except for ganglioside G, than ganglioside G M2 .