iso‐Fatty Acid Metabolism in Caenorhabditis elegans’ Ceramide Biosynthesis

Abstract

Ceramide biosynthesis and its connection to iso‐fatty acid metabolism in the model organism Caenorhabditis elegans was investigated using a combination of reverse genetics and comparative ESI‐(+)‐HR‐MSe ceramide profiling along with incorporation experiments with bacterial mutants specifically enriched with isotopically labeled branched‐chain amino acids or branched‐chain fatty acids. Incorporation of a l‐leucine‐derived isovalerate unit into the conserved d17 : 1iso sphingosine building block proceeds through elo‐5 dependent chain elongation and depends on peroxisomal β‐oxidation by the 3‐ketoacyl‐CoA thiolase daf‐22, although ceramide profiles of N2 wildtype and daf‐22(ok693) are indistinguishable. Biosynthesis of the homologous N‐iso‐acyl moieties also depends on l‐leucine and isovalerate chain elongation but proceeds independently of elo‐5 and daf‐22. Biosynthesis of the dominating N‐docosanoyl moiety depends on elo‐3‐catalyzed chain elongation of bacteria‐derived palmitic acid, whereas the N‐tetracosanoyl moiety is derived from de novo lipogenesis.