Figure 1.

Early glycosphingolipid biosynthesis in ER and Golgi complex. Lipids outside the yellow organelles are synthesized on the cytosolic surface. Blue boxes indicate the translocation of a lipid across the membrane. Cer, ceramide; Ga, gala; Gal, galactose; GalNAc, N-acetylgalactosamine; Gb, globo; Gg, ganglio; Glc, glucose; GlcNAc, N-acetylglucosamine; iGb, isoglobo; NeuAc, neuraminic/sialic acid; SM, sphingomyelin. For nomenclature of glycolipids, see ref. 26. The synthesis of the ganglioside GM3 (3) is indicated in red. (a) GlcCer is synthesized at two locations, or (b) transport competes with translocation.