Figure 2

Lipid degradation and lysosomal lipid storage diseases. A) Sequential degradation pathways of selected (glyco)sphingolipids in which hydrolytic enzymes catalyzing SL degradation often need the assistance of an additional protein (GM2-activator or one of 3 saposins: SAP-B,-C,-D as indicated). B) Cholesterol storage in the late endosomal/lysosomal compartment due to mutated NPC1 or NPC2 proteins mediating its transport to post-lysosomal compartments (e.g. the ER). The names of respective diseases are indicated. Cer, Ceramide, Gal, D-galactose; GalNAc, N-Acetyl-D-galactosamine; Chol, cholesterol; Glc, D-glucose; GlcCer, glucosylceramide; LacCer, lactosylceramide; the terminology used for gangliosides GM1, GM2, GM3 is that of Svennerholm [106]; SM, sphingomyelin, Sph, sphingosine, Cerase, ceramidase; GlcCerase, Glucosylceramide-β-glucosidase; SMase, sphingomyelinase; SAP, sphingolipid activator protein, saposin. For detailed schemes on SL metabolism see [8].