Sphingosine kinase 1 catalyzes the phosphorylation of sphingosine to form sphingosine 1-phosphate (spp)(sphingosine + ATP = sphingosine 1-phosphate + ADP), a lipid mediator with both intra- and extracellular functions. also acts on d-erythro-sphingosine and to a lesser extent sphinganine, but not other lipids, such as d,l-threo-dihydrosphingosine, n,n-dimethylsphingosine, diacylglycerol, ceramide, or phosphatidylinositol. The long form of sphingosine kinase 1, an N-terminal extension, is responsible for FceRI-mediated calcium mobilization and may play a role in other ligand mediated signaling events.