title: An oleate 12-hydroxylase from Ricinus communis L. is a fatty acyl desaturase homolog.
abstract: Recent spectroscopic evidence implicating a binuclear iron site at the reaction center of fatty acyl desaturases suggested to us that certain fatty acyl hydroxylases may share significant amino acid sequence similarity with desaturases. To test this theory, we prepared a cDNA library from developing endosperm of the castor-oil plant (Ricinus communis L.) and obtained partial nucleotide sequences for 468 anonymous clones that were not expressed at high levels in leaves, a tissue deficient in 12-hydroxyoleic acid. This resulted in the identification of several cDNA clones encoding a polypeptide of 387 amino acids with a predicted molecular weight of 44,407 and with approximately 67% sequence homology to microsomal oleate desaturase from Arabidopsis. Expression of a full-length clone under control of the cauliflower mosaic virus 35S promoter in transgenic tobacco resulted in the accumulation of low levels of 12-hydroxyoleic acid in seeds, indicating that the clone encodes the castor oleate hydroxylase. These results suggest that fatty acyl desaturases and hydroxylases share similar reaction mechanisms and provide an example of enzyme evolution.
authors.affiliation: Department of Plant Biology, Carnegie Institution of Washington, Stanford, CA 94305-4101, USA.
authors.forename: F J
authors.initials: FJ
authors.lastname: van de Loo
authors.forename: P
authors.initials: P
authors.lastname: Broun
authors.forename: S
authors.initials: S
authors.lastname: Turner
authors.forename: C
authors.initials: C
authors.lastname: Somerville
mesh_terms: D001483:Base Sequence; D015152:Blotting, Northern; D015139:Blotting, Southern; D018076:DNA, Complementary / Q000235:genetics; D044943:Fatty Acid Desaturases / Q000235:genetics; D015723:Gene Library; D006899:Mixed Function Oxygenases / Q000235:genetics*; D008969:Molecular Sequence Data; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D011994:Recombinant Proteins / Q000096:biosynthesis; D012278:Ricinus / Q000201:enzymology* / Q000235:genetics; D012639:Seeds / Q000201:enzymology / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014026:Nicotiana / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D009829:Oleic Acids; D010940:Plant Proteins; D011994:Recombinant Proteins; D019301:Oleic Acid; D006899:Mixed Function Oxygenases; C094812:phosphatidylcholine 12-monooxygenase; D044943:Fatty Acid Desaturases; C021904:Phosphatidylcholine desaturase; D044925:Oxidoreductases Acting on CH-CH Group Donors