chemical ligand sphingolipid second messenger sphingosine-1-phosphate IMR:0100179 KEGG:C060506 KEGG:C06124 S1P Sphingolipid mediators, such as sphingosine 1-phosphate (S1P), ceramide, and sphingosine are derived by the enzymatic breakdown of sphingomyelin, an abundant membrane phospholipid. S1P is an evolutionarily conserved bioactive lipid mediator with potent effects on multiple organ systems. molecule_role lipid mediator