Metabolism of long-chain bases of sphingolipids and fatty acid α-oxidation

Abstract

Sphingolipids are one of the major lipid species constituting eukaryotic membranes: ceramide, their hydrophobic backbone, is composed of a long-chain base (LCB) and a fatty acid. LCB degradation is an important process for sphingolipid homeostasis. Recently, we reported detailed metabolic pathways for LCBs, including the specific reactions and genes involved. Among them, the LCB phytosphingosine, which has a C4 hydroxyl group, was found to undergo fatty acid α-oxidation during its metabolism, and be converted to odd-numbered fatty acids. To date, fatty acid α-oxidation has been thought to occur in peroxisomes, but our finding was completely new in that the observed α-oxidation takes place in the endoplasmic reticulum. In this review, we introduce the structure of sphingolipids and the latest findings about LCB metabolism and fatty acid α-oxidation, including from our own analyses using yeast and mammalian cells. Furthermore, based on our findings, we discuss the metabolism of LCBs in plants.