Sphingosine (SPH) is a long-chain aliphatic compound with an acyclic carbon skeleton, typically featuring a 2-amino-1,3-diol functional group. The primary SPH in mammalian tissues are sphingosine (2S,3R-d-erythro-2-amino-1,3-octadec-4E-ene-diol), sphinganine (2S,3R-d-erythro-2-amino-1,3-octadecane diol), and 4-hydroxy-sphinganine (2S,3S,4R-erythro-2-amino-1,3,4-octadecanetriol). In yeast, the primary sphingoid bases are dihydrosphingosine and phytosphingosine.