Sphingolipid metabolic pathways and enzymes described in mammalian cells. Serine and palmityl-CoA will be utilized to synthesize 3-ketodihydrosphinganine generating the sphingoid backbone (blue). The subsequent dehydrogenation and acylation will produce dihydroceramide which contains a fatty amide (green). Dihydroceramide can be desaturated to produce ceramide. Ceramide can either be used for catabolism to generate sphingosine and sphingosine-1-phosphate or one of many complex sphingolipids with an additional head group (purple). All synthesis reactions producing complex sphingolipids are reversible, while the sphingosine-1-phosphate catabolic reaction is not. Abbreviations: Cer1PP, ceramide-1-phosphate phosphatase; Cerases, acid-, alkaline-, and neutral-ceramidase; CerK, ceramide kinase; CerS1-6, ceramide synthase 1-6; DHCD1, dihydroceramide desaturase 1; GalCerase, galactosylceramidase; GluCerase, glucosylceramidase; KDSR, ketodihydrosphingosine reductase; LacCS, lactosylceramide synthase; S1PL: sphingosine-1-phosphate lyase; S1PP: sphingosine-1-phosphate phosphatase; SMases, acid-, alkaline-, and neutral-sphingomyelinase; SMS1/2, sphingomyelin synthase 1/2; SPK, sphingosine kinase; SPT, serine palmitoyltransferase; UGalCGT, UDP-galactose-ceramide galactosyltransferase; UGluCGT, UDP-glucose-ceramide glucosyltransferase.