cDNA cloning and characterization of human Δ5-desaturase involved in the biosynthesis of arachidonic acid

Abstract

Two human expressed sequence tag (EST) cDNA sequences with identity with Delta(5)- and Delta(6)-desaturases from a filamentous fungus, Mortierella alpina, were identified from the LifeSeq(R) database of Incyte Pharmaceuticals, Inc. (Palo Alto, CA, U.S.A.). An oligonucleotide complementary to the 3' EST cDNA sequences was used to screen human liver cDNA using rapid amplification of cDNA ends (RACE)-PCR. The amplified DNA fragment had 98% identity with a putative open reading frame (ORF) predicted from a human genomic sequence, and encoded 444 amino acids. Expression of this ORF in mouse fibroblast cells demonstrated that the encoded protein was a Delta(5)-desaturase, as determined by the conversion of dihomo-gamma-linolenic acid (C(20:3,n-6)) into arachidonic acid (C(20:4,n-6)). The human Delta(5)-desaturase contained a predicted N-terminal cytochrome b(5)-like domain, as well as three histidine-rich domains. A tissue expression profile revealed that this gene is highly expressed in fetal liver, fetal brain, adult brain and adrenal gland. A search of the existing databases led to localization of this ORF within a 14 kb interval flanked by the flap endonuclease-1 (FEN1) and vitelliform macular dystrophy (Best's disease; VMD2) loci of chromosome 11q12.

Zebrafish cDNA Encoding Multifunctional Fatty Acid Elongase Involved in Production of Eicosapentaenoic (20:5n-3) and Docosahexaenoic (22:6n-3) Acids

“…This is in contrast to all other vertebrate and eukaryotic systems studied in which desaturase activities are encoded by disparate genes (Aki et al, 1999;Cho et al, 1999a,b;Leonard et al, 2000a;Michaelson et al, 1998;Napier et al, 1998;Watts and Browse, 1998).…”

Characterization and comparison of fatty acyl Δ6 desaturase cDNAs from freshwater and marine teleost fish species

“…Full-length cDNAs for Δ6 desaturases have been isolated from the filamentous fungus Mortierella alpina (Huang et al, 1999), the nematode Caenorhabditis elegans (Napier et al, 1998), rat (Aki et al, 1999), mouse and human (Cho et al, 1999a). Fatty acid Δ5 desaturase genes have been isolated from M. alpina (Michaelson et al, 1998a), C. elegans (Michaelson et al, 1998b;Watts and Browse, 1999) and human (Cho et al, 1999b;Leonard et al, 2000). Using extant sequence information, we isolated a cDNA from the freshwater zebrafish (Danio rerio) with high similarity to mammalian Δ6 desaturase genes (Hastings et al, 2001).…”

Metabolism and Functions of Lipids and Fatty Acids in Teleost Fish

“…Full length cDNAs for Δ6 fatty acid desaturases have been isolated from the nematode worm Caenorhabditis elegans , rat (Aki et al, 1999), mouse and human (Cho et al, 1999a). Fatty acid Δ5 desaturase genes have been isolated from C. elegans (Michaelson et al, 1998;Watts and Browse, 1999) and human (Cho et al, 1999b;Leonard et al, 2000a). Very recently, a fatty acid desaturase has been cloned from zebrafish that has been shown to have both Δ6 and Δ5 desaturase activities (Hastings et al, 2001).…”