Songsri KaewsuwanEdgar B. CahoonPierre François PerroudChanpen WiwatNathinee PanvisavasRalph S. QuatranoDavid J. CoveNuntavan BunyapraphatsaraMahidol UniversityDonald Danforth Plant Science CenterWashington University in St. Louis2018-08-202018-08-202006-08-04Journal of Biological Chemistry. Vol.281, No.31 (2006), 21988-219971083351X002192582-s2.0-33746857255https://repository.li.mahidol.ac.th/handle/123456789/22994The moss Physcomitrella patens contains high levels of arachidonic acid and lesser amounts of eicosapentaenoic acid. Here we report the identification and characterization of a Δ5-desaturase from P. patens that is associated with the synthesis of these fatty acids. A full-length cDNA for this desaturase was identified by data base searches based on homology to sequences of known Δ5-desaturase cDNAs from fungal and algal species. The resulting P. patens cDNA encodes a 480-amino acid polypeptide that contains a predicted N-terminal cytochrome b5-like domain as well as three histidine-rich domains. Expression of the enzyme in Saccharomyces cerevisiae resulted in the production of the Δ5-containing fatty acid arachidonic acid in cells that were provided di-homo-γ-linolenic acid. In addition, the expressed enzyme generated Δ5-desaturation products with the C20 substrates ω-6 eicosadienoic and ω-3 eicosatrienoic acids, but no products were detected with the C18 fatty acid linoleic and α-linolenic acids or with the C22 fatty acid adrenic and docosapentaenoic acids. When the corresponding P. patens genomic sequence was disrupted by replacement through homologous recombination, a dramatic alteration in the fatty acid composition was observed, i.e. an increase in di-homo-γ-linolenic and eicosatetraenoic acids accompanied by a concomitant disappearance of the Δ5-fatty acid arachidonic and eicosapentaenoic acids. In addition, overexpression of the P. patens cDNA in protoplasts isolated from a disrupted line resulted in the restoration of arachidonic acid synthesis.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyArticleSCOPUS10.1074/jbc.M603022200