Biosynthesis of sphingolipids: dihydroceramide and not sphinganine is desaturated by cultured cells.
Radioactively labeled N-[1-14C]-octanoyl-sphinganine and D-erythro-[3-3H]-sphinganine were administered in parallel experiments to neuroblastoma cells B 104. A time dependent formation of ceramide with a double bond in its sphingoid backbone was observed in both cases. In the presence of fumonisin B1 (25 microM), a strong inhibitor of sphinganine N-acyltransferase, desaturated ceramide was formed only when cells were fed with N-[1-14C]-octanoyl-sphinganine but not with [3-3H]-sphinganine. Thus, the introduction of the double bond occurs only at the level of dihydroceramide, after N-acylation of sphinganine. It is now obvious that sphingosine is not a biosynthetic intermediate but exclusively a catabolic product of cellular sphingolipids.
Rother
J
J
Institut für Organische Chemie und Biochemie, Universität Bonn, Germany.
van Echten
G
G
Schwarzmann
G
G
Sandhoff
K
K
D000818:Animals; D002274:Carcinogens, Environmental / Q000494:pharmacology; D002518:Ceramides / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D037341:Fumonisins; D007700:Kinetics; D009183:Mycotoxins / Q000494:pharmacology; D009447:Neuroblastoma; D010084:Oxidation-Reduction; D016339:Spectrometry, Mass, Fast Atom Bombardment; D013107:Sphingolipids / Q000096:biosynthesis*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism; D014407:Tumor Cells, Cultured
D002274:Carcinogens, Environmental; D002518:Ceramides; D037341:Fumonisins; D009183:Mycotoxins; D013107:Sphingolipids; C056933:fumonisin B1; D013110:Sphingosine; C005682:safingol