title: Biochemistry and site-directed mutational analysis of Delta7-sterol-C5(6)-desaturase.
abstract: This report describes recent work on the process of desaturation at C5(6) of sterol precursors in plants. Biochemical characterization of the plant Delta(7)-sterol C5(6)-desaturase (5-DES) indicates that the enzyme system involved shows important similarities to the soluble and membrane-bound non-haem iron desaturases found in eukaryotes, including cyanide and hydrophobic chelators sensitivity, CO resistance and a requirement for exogenous reductant and molecular oxygen. Site-directed mutational analysis of highly conserved residues in 5-DES indicated that eight histidine residues from three histidine-rich motifs were essential for the catalysis, possibly by providing the ligands for a putative Fe centre. This mutational analysis also revealed the catalytic role of the functionally conserved Thr-114.
authors.affiliation: Département Isoprénoïdes, Institut de Biologie Moléculaire des Plantes, CNRS FRE 2161, 28 rue Goethe 67083, Strasbourg Cedex, France. enzymo@bota-ulp.u-strasbg.fr
authors.forename: A
authors.initials: A
authors.lastname: Rahier
authors.forename: P
authors.initials: P
authors.lastname: Benveniste
authors.forename: T
authors.initials: T
authors.lastname: Husselstein
authors.forename: M
authors.initials: M
authors.lastname: Taton
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D017360:Arabidopsis / Q000201:enzymology*; D002384:Catalysis; D017124:Conserved Sequence; D006639:Histidine; D006801:Humans; D007501:Iron / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010947:Plants, Toxic; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000201:enzymology; D003313:Zea mays / Q000201:enzymology*
chemical_list: D011994:Recombinant Proteins; D006639:Histidine; D007501:Iron; D010088:Oxidoreductases; C039306:sterol delta-5 desaturase