Biosynthesis of very long chain fatty acids by the sciatic nerve of the rabbit

The alkanes, a new class of neurolipids, are accumulated in the brain myelin when compared to the other brain subfractions [l--4]. The role of these hydrophobic substances in the myelin formation is far from clear. It appears that alkanes are required for a correct myelination, since the remaining myelin of the Quaking mutant, which bears a defect of myelin formation, presents only 30%total alkanes found in the wild type [l]. The peripheral nervous system contains also large amounts of alkanes [S]. By using a microsomal fraction from rabbit sciatic nerve, we established that the alkanes can be synthesized by mammalians, contrary to the widely accepted idea that these substances are due to an exogenous contamination [5]. The nature of the cofactor requirements and of the substrates leading to alkane synthesis in subcellular fractions from rabbit sciatic nerve suggested that alkanes are biosynthesized by decarboxylation of very long chain fatty acids [5]. That hypothesis would remain speculative until a synthesis of these acids in the peripheral nervous system has been demonstrated. In fact saturated very long chain fatty acids are well-known components of the lipids of the brain myelin [6-l 71, and they are assumed to play a great role in its stability and cohesiveness [6,7 ,I 8-221. Their biosynthesis has been studied in brain subfractions [23-291.