Figure 4.

Brief biochemistry of sphingolipids. Ceramide is at the center of the biochemical pathways of sphingolipids. Enzymes are written in blue in the figure. De novo synthesis of ceramide from palmitate and serine takes place in the endoplasmic reticulum. It can be converted to sphingomyelin by the transfer of phosphocholine from phosphatidylcholine by sphingomyelin synthase located in the Golgi complex or at the plasma membrane. By cleaving the fatty acid from ceramide, ceramidase produces sphingosine that can be further phosphorylated to sphingosine-1-phosphate. Addition of glucose to ceramide results in glucocerebroside from which gangliosides with complex oligosaccharides can be synthesized. The nomenclature of gangliosides is briefly summarized in the insert on the left.