Figure 1.

Sphingolipid metabolism pathway. De novo (light green arm) sphingolipid biosynthesis begins with the condensation of serine and palmitoyl-CoA, which is catalyzed by the serine palmitoyltransferase enzyme. Its product, 3-ketosphinganine is enzymatically reduced to sphinganine or dihydrosphingosine by 3-ketosphinganine reductase. Sphinganine and fatty acyls then synthesize dihydroceramides under the regulation of the dihydro ceramide synthases (CerS) that are then reduced by dihydroceramide desaturase to produce ceramides of different acyl-chain lengths. Ceramide can also be metabolized via other enzymes in the salvage (light blue and pink arms), sphingomyelin hydrolysis (dark green arm) pathways.