FIG 1.
Sphingolipid metabolic pathway. Sphingolipid biosynthesis leads to the formation of ceramide, the main building block of complex sphingolipids. Ceramide is degraded to sphingosine. Sphingosine is phosphorylated by sphingosine kinases, leading to formation of S1P, which has intracellular activities and also serves as a ligand for S1P receptors (S1PR1–5). S1P can be dephosphorylated by specific and nonspecific lipid phosphatases, regenerating sphingosine. Alternatively, S1P can be irreversibly degraded by sphingosine-1-phosphate lyase (S1P lyase), which controls the sole exit point of sphingolipid metabolism. S1P catabolism by sphingosine-1-phosphate lyase results in formation of hexadecenal and ethanolamine phosphate. CoA indicates coenzyme A.