In the genome of Arabidopsis thaliana, two genes were identified encoding i
soenzymes for C4-hydroxylation of long chain bases (LCB) in plant sphingoli
pids, Both predicted proteins consist of 258 amino acid residues (77% ident
ity) which show sequence similarity to di-iron-binding enzymes, such as Sur
2p and Erg3p from yeast, involved in oxygen-dependent lipid modifications.
Heterologous expression of these genes in a yeast sur2 Delta -null mutant l
acking 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 spe
ctroscopy, gas-liquid chromatography-mass spectrometry and H-1-nuclear magn
etic resonance spectroscopy, These results represent the first functional i
dentification 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 Fe
deration of European Biochemical Societies.