title: Identification of a novel C22-∆4-producing docosahexaenoic acid (DHA) specific polyunsaturated fatty acid desaturase gene from Isochrysis galbana and its expression in Saccharomyces cerevisiae.
abstract: Isochrysis galbana, produces long chain polyunsaturated fatty acids including docosahexaenoic acid (DHA, 22:6n-3). A novel gene (IgFAD4-2), encoding a C22-∆4 polyunsaturated fatty acid specific desaturase, has been isolated and characterized from I. galbana. A full-length cDNA of 1,302 bp was cloned by LA-PCR technique. The IgFAD4-2 encoded a protein of 433 amino acids that shares 78 % identity with a previously reported ∆4-desaturase (IgFAD4-1) from I. galbana. The function of IgFAD4-2 was deduced by its heterologous expression in Saccharomyces cerevisiae, which then desaturated docosapentaenoic acid (DPA, 22:5n-3) to DHA. The conversion ratio of DPA to DHA was 34 %, which is higher than other ∆4-desaturases cloned from algae. However, IgFAD4-2 did not catalyze the desaturation or elongation reactions with other fatty acids. These results confirm that IgFAD4-2 has C22-∆4-PUFAs-specific desaturase activity.
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Department of Microbiology, Nankai University, Tianjin, China. bluelovely123@yahoo.com.cn
authors.forename: Tonglei
authors.initials: T
authors.lastname: Shi
authors.forename: Aiqun
authors.initials: A
authors.lastname: Yu
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.forename: Xiuyuan
authors.initials: X
authors.lastname: Ou
authors.forename: Laijun
authors.initials: L
authors.lastname: Xing
authors.forename: Mingchun
authors.initials: M
authors.lastname: Li
mesh_terms: D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D016000:Cluster Analysis; D004281:Docosahexaenoic Acids / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D058087:Haptophyta / Q000201:enzymology* / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017386:Sequence Homology, Amino Acid
chemical_list: D004281:Docosahexaenoic Acids; D044943:Fatty Acid Desaturases