Dihydroceramide: Sphinganine Δ4-desaturase and C4-hydroxylase

Abstract

N-acylsphingenine (ceramide) and N-acyl-4-hydroxy- sphinganine (phytoceramide) are intermediates in glycosphingolipid and sphingomyelin biosynthesis. Ceramide has attracted attention because it is a signaling molecule involved in apoptosis. The genes for N-acylsphinganine, sphinganine ω4-desaturase and C4-hydroxylase, are responsible for the biosynthesis of ceramide and dihydroceramide. These genes were identified in 2002 through exhaustive search of plant and yeast desaturases, but this review will address primarily the desaturases and hydroxylases of animal origin, particularly the distribution and functions of ceramide and phytoceramide in animal tissues. Ceramide-containing sphingolipids are widely distributed, whereas phytoceramide-containing sphingolipids are limited tissues in the intestine, kidney and skin. Distribution appears to be regulated by the expression of Δ4-desaturase and C4-hydroxylase enzymes. Recent developments concerning these two enzymes are discussed here. © Springer-Verlag Tokyo 2006. All rights reserved.