Sphingomyelin

Sphingomyelin (SPH, ˌsfɪŋɡoˈmaɪəlɪn) is a type of sphingolipid found in animal cell membranes, especially in the membranous myelin sheath that surrounds some nerve cell axons. It usually consists of phosphocholine and ceramide, or a phosphoethanolamine head group; therefore, sphingomyelins can also be classified as sphingophospholipids.^[1][2] In humans, SPH represents ~85% of all sphingolipids, and typically makes up 10–20 mol % of plasma membrane lipids.

Sphingomyelin was first isolated by German chemist Johann L.W. Thudicum in the 1880s.^[3] The structure of sphingomyelin was first reported in 1927 as N-acyl-sphingosine-1-phosphorylcholine.^[3] Sphingomyelin content in mammals ranges from 2 to 15% in most tissues, with higher concentrations found in nerve tissues, red blood cells, and the ocular lenses. Sphingomyelin has significant structural and functional roles in the cell. It is a plasma membrane component and participates in many signaling pathways. The metabolism of sphingomyelin creates many products that play significant roles in the cell.^[3]