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Identification of a cDNA encoding a novel C18‐Δ 9 polyunsaturated fatty acid‐specific elongating activity from the docosahexaenoic acid (DHA)‐producing microalga, Isochrysis galbana 1
Author(s) -
Qi Baoxiu,
Beaudoin Frédéric,
Fraser Tom,
Stobart A.Keith,
Napier Johnathan A,
Lazarus Colin M
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(01)03247-1
Subject(s) - docosahexaenoic acid , isochrysis galbana , polyunsaturated fatty acid , biochemistry , linoleic acid , biology , eicosapentaenoic acid , linolenic acid , yeast , fatty acid , complementary dna , gene , algae , botany
Isochrysis galbana , a marine prymnesiophyte microalga, is rich in long chain polyunsaturated fatty acids such as docosahexaenoic acid (C22:6n‐3, Δ 4,7,10,13,16,19 ). We used a polymerase chain reaction‐based strategy to isolate a cDNA, designated IgASE1 , encoding a polyunsaturated fatty acid‐elongating activity from I. galbana . The coding region of 263 amino acids predicts a protein of 30 kDa that shares only limited homology to animal and fungal proteins with elongating activity. Functional analysis of IgASE1 , by expression in Saccharomyces cerevisiae , was used to determine its activity and substrate specificity. Transformed yeast cells specifically elongated the C18‐Δ 9 polyunsaturated fatty acids, linoleic acid (C18:2n‐6, Δ 9,12 ) and α‐linolenic acid (C18:3n‐3, Δ 9,12,15 ), to eicosadienoic acid (C20:2n‐6, Δ 11,14 ) and eicosatrienoic acid (C20:3n‐3, Δ 11,14,17 ), respectively. To our knowledge this is the first time such an elongating activity has been functionally characterised. The results also suggest that a major route for eicosapentaenoic acid (C20:5n‐3, Δ 5,8,11,14,17 ) and docosahexaenoic acid syntheses in I. galbana may involve a Δ 8 desaturation pathway.