ABSTRACT
Sphingomyelin (SM) was initially described and partially characterized by Thudichum, and the chemical structure was eventually elucidated in a series of studies culminating some 70 years later. The original description of SM biosynthesis was a reaction between cytidine diphosphate choline and the primary hydroxyl of ceramide in analogy to phosphatidylcholine biosynthesis from diacylglycerol. All evidence to date is consistent with a phospholipase C type reaction or Smase as the first step in SM catabolism. A phospholipase-C type enzyme that hydrolyzes both micellar SM and membrane SM, and which has no demonstrable activity with phosphatidylcholine, has been purified from Staphylococcus aureus. A rapid perusal of the indices of scientific articles in the past decade will show that SM has always been of interest, but has occupied less attention than the phosphoglycerides and glycolipids. The major unresolved question in the biosynthesis of SM remains the reaction mechanism for the transfer of P-choline from phosphatidylcholine to ceramide.
