Identification and characterization of new Δ-17 fatty acid desaturases.
ω-3 fatty acid desaturase is a key enzyme for the biosynthesis of ω-3 polyunsaturated fatty acids via the oxidative desaturase/elongase pathways. Here we report the identification of three ω-3 desaturases from oomycetes, Pythium aphanidermatum, Phytophthora sojae, and Phytophthora ramorum. These new ω-3 desaturases share 55 % identity at the amino acid level with the known Δ-17 desaturase of Saprolegnia diclina, and about 31 % identity with the bifunctional Δ-12/Δ-15 desaturase of Fusarium monoliforme. The three enzymes were expressed in either wild-type or codon optimized form in an engineered arachidonic acid producing strain of Yarrowia lipolytica to study their activity and substrate specificity. All three were able to convert the ω-6 arachidonic acid to the ω-3 eicosapentanoic acid, with a substrate conversion efficiency of 54-65 %. These enzymes have a broad ω-6 fatty acid substrate spectrum, including both C18 and C20 ω-6 fatty acids although they prefer the C20 substrates, and have strong Δ-17 desaturase activity but weaker Δ-15 desaturase activity. Thus, they belong to the Δ-17 desaturase class. Unlike the previously identified bifunctional Δ-12/Δ-15 desaturase from F. monoliforme, they lack Δ-12 desaturase activity. The newly identified Δ-17 desaturases could use fatty acids in both acyl-CoA and phospholipid fraction as substrates. The identification of these Δ-17 desaturases provides a set of powerful new tools for genetic engineering of microbes and plants to produce ω-3 fatty acids, such as eicosapentanoic acid and docosahexanoic acid, at high levels.
Biochemical Science and Engineering, Central Research and Development, E. I. DuPont de Nemours, Experimental Station, Wilmington, DE 19880, USA. zhixiong.xue@usa.dupont.com
Zhixiong
Z
Xue
Hongxian
H
He
Dieter
D
Hollerbach
Daniel J
DJ
Macool
Narendra S
NS
Yadav
Hongxiang
H
Zhang
Bogdan
B
Szostek
Quinn
Q
Zhu
D000595:Amino Acid Sequence; D016718:Arachidonic Acid / Q000378:metabolism; D001711:Biotransformation; D003001:Cloning, Molecular; D015118:Eicosapentaenoic Acid / Q000378:metabolism; D044943:Fatty Acid Desaturases / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010838:Phytophthora / Q000201:enzymology* / Q000235:genetics; D011775:Pythium / Q000201:enzymology* / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D044762:Saprolegnia / Q000201:enzymology / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D025062:Yarrowia / Q000235:genetics
D011994:Recombinant Proteins; D016718:Arachidonic Acid; D015118:Eicosapentaenoic Acid; D044943:Fatty Acid Desaturases; C078565:omega-3 fatty acid desaturase