Sphingomyelin: Metabolism, chemical synthesis, chemical and physical properties

Sphingomyelin (SPM; N-acyl sphingosine-1-phosphocholine; ceramide-1-phosphocholine) is a major lipid constituent of animal tissues. When isolated from various natural sources, sphingomyelin varies in two of its components: sphingosine (long-chain base (LCB)) and the fatty acyl residues. With the development of chromatographic and analytical procedures, several LCBs have been characterized. The compositional analysis of SPM requires its complete hydrolysis to intact LCB and fatty acid, but most of the procedures used for the degradation of sphingomyelin lead to incomplete dephosphorylation of the base. This is so in case of hydrolysis by HCl in anhydrous methanol or in methanol–water mixtures. Hydrolysis by HCl also results in the formation of several derivatives of sphingosine, whereas alkaline hydrolysis results in a low yield of sphingosine bases. These problems can be overcome by initial dephosphorylation of SPM using either phospholipase C of Clostridium perfringens or by hydrofluoric acid; neither treatment alters the stereochemical configuration of the sphingosine base. These procedures yield ceramide (N-acylsphingosine), which is then completely hydrolyzed by alkali to LCB and fatty acids.