Studies on the biosynthesis of ceramide. Does the reversed ceramidase reaction yield ceramides?

During studies on the biosynthetic pathways of sphingomyelin, the condensation reaction between free fatty acids and sphingenine to ceramide catalysed in the reversed ceramidase reaction as proposed by Gatt (J. Biol. Chem. 238, PC 3131-3133 (1963) was reinvestigated. Radioactive long-chain fatty acids (palmitate and oleate) condense with ethanolamine, one of the buffer components of the original studies and yield N-acylethanolamine. N-Palmitoylethanolamine was isolated on a preparative scale from incubation mixtures and identified directly and also after derivatization by mass spectroscopy and comparison with the authentic synthetic compound. It is concluded that only the acyl-CoA-dependent ceramide synthesis is of biological significance.