title: Gene cloning and functional analysis of a second delta 6-fatty acid desaturase from an arachidonic acid-producing Mortierella fungus.
abstract: We demonstrated that Mortierella alpina 1S-4 has two delta 6-desaturases, which are involved in the desaturation of linoleic acid to gamma-linolenic acid. For one of the two delta 6-desaturases, designated as delta 6I, gene cloning and its heterologous expression in a fungus, Aspergillus oryzae, has previously been reported. In addition, we indicated in this paper that there is an isozyme of the two delta 6-desaturases, designated as delta 6II, in M. alpina 1S-4. The predicted amino acid sequences of the Mortierella delta 6-desaturases were similar to those of ones from other organisms, i.e. borage and Caenorhabditis elegans, and had a cytochrome b5-like domain at the N-terminus, being different from the yeast delta 9-desaturase, which has the corresponding domain at the C-terminus. The full-length delta 6II cDNA was expressed in A. oryzae, resulting in the accumulation of gamma-linolenic acid (which was not detected in the control Aspergillus) up to 37% of the total fatty acids. The analysis of real-time quantitative PCR (RTQ-PCR) showed that the quantity of delta 6I RNA was 2.4-, 9-, and 17-fold higher than that of delta 6II RNA on 2, 3, and 4 days in M. alpina 1S-4, respectively. M. alpina 1S-4 is the first fungus to be confirmed to have two functional delta 6-desaturase genes.
authors.affiliation: Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Kitashirakawa-oiwakecho, Sakyo-ku, Kyoto 606-8502, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Sakuradani
authors.forename: Sakayu
authors.initials: S
authors.lastname: Shimizu
mesh_terms: D000595:Amino Acid Sequence; D016718:Arachidonic Acid / Q000096:biosynthesis; D001236:Aspergillus oryzae / Q000235:genetics; D003001:Cloning, Molecular; D044943:Fatty Acid Desaturases / Q000235:genetics*; D005800:Genes, Fungal; D007527:Isoenzymes / Q000235:genetics; D050602:Linoleoyl-CoA Desaturase; D008969:Molecular Sequence Data; D020094:Mortierella / Q000201:enzymology* / Q000378:metabolism; D012313:RNA / Q000032:analysis
chemical_list: D007527:Isoenzymes; D016718:Arachidonic Acid; D012313:RNA; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase