Functional characterization of sphingolipid C4-hydroxylase genes from Arabidopsis thaliana

In the genome of Arabidopsis thaliana, two genes were identified encoding isoenzymes for C4-hydroxylation of long chain bases (LCB) in plant sphingolipids, Both predicted proteins consist of 258 amino acid residues (77% identity) which show sequence similarity to di-iron-binding enzymes, such as Sur2p and Erg3p from yeast, involved in oxygen-dependent lipid modifications. Heterologous expression of these genes in a yeast sur2 Delta -null mutant lacking C4-LCB hydroxylation resulted in the formation of D-ribo-C-18- and -C-20-phytosphinganine. The identity and stereochemical configuration of the isolated trihydroxybases was confirmed by electrospray ionization-mass spectroscopy, gas-liquid chromatography-mass spectrometry and H-1-nuclear magnetic resonance spectroscopy, These results represent the first functional identification of SUR2 genes from plants as well as from any organism other than yeast. (C) 2001 Published by Elsevier Science B,V, on behalf of the Federation of European Biochemical Societies.