ABSTRACT
In contrast to glycerolipids that have fatty acids esterified to sn-glycerol-3-phosphate, sphingolipids consist of a long-chain base having a single amide-linked fatty acid. Complex sphingolipids are formed by the addition of polar groups such as phosphocholine or one or more sugar residues to the relatively nonpolar N-acyl long-chain base. Glucosylceramides and related sphingolipids are minor components in lipid extracts of plant tissues, typically accounting for less than 5% of the total lipid. The biosynthetic pathway for complex sphingolipids begins with the synthesis of the long-chain base sphinganine. The first step in C18 long-chain base synthesis is the condensation of L-serine with palmitoyl-coenzyme (CoA), catalyzed by serine palmitoyltransferase. Synthesis of ceramide involves formation of an amide bond via condensation of fatty acid with the amino group of long-chain base. Synthesis of ceramides using acyl-CoA as the donor was demonstrated in brain and liver homogenates and microsomal preparations from brain.
