Sphingosine (d16:1), an unconventional sphingolipid, is synthesized through enzymatic reactions starting with the condensation of myristoyl-CoA and serine by serine palmitoyltransferase long-chain base subunit 3 (SPTLC3), which shows a preference for myristoyl-CoA. This compound is found in minute quantities in its free form in human plasma and as a component of various plasma sphingolipids, such as sphingosine-1-phosphate, ceramides, sphingomyelins, and in brain cerebrosides, albeit at lower concentrations than the more common d18:1 sphingoid base. Sphingosine (d16:1) acts as an inhibitor of PKC in mixed micelle assays and diminishes superoxide production triggered by phorbol 12-myristate 13-acetate in isolated human neutrophils, as well as inhibiting the growth of CHO cells with IC50 values of 1 and 3.2 µM, respectively. Additionally, the concentration of sphingolipids containing sphingosine (d16:1) in the plasma is linked to the dietary consumption of saturated fatty acids and protein among ethnic Chinese populations.