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Isolation of Delta12 and omega3-fatty acid desaturase genes from the yeast Kluyveromyces lactis and their heterologous expression to produce linoleic and alpha-linolenic acids in Saccharomyces cerevisiae.

Two clones with homology to known fatty acid desaturase genes were isolated from the yeast Kluyveromyces lactis. The first gene, which we designate KlFAD2, consists of 411 amino acids with an overall identity of 73.0% to FAD2 from Saccharomyces kluyveri. It exhibited Delta12 fatty acid desaturase activity when expressed in S. cerevisiae under the control of ADH1 promoter and produced endogenous linoleic acid. The second clone, which we designate KlFAD3, consists of 415 amino acids with an overall identity of 79.3% to FAD3 from S. kluyveri. It exhibited omega3 fatty acid desaturase activity in S. cerevisiae when expressed under the control of ADH1 promoter in the presence of the exogenous substrate linoleic acid and produced alpha-linolenic acid. Co-expression of KlFAD2 and KlFAD3 resulted in the endogenous production of both linoleic and alpha-linolenic acids. The yield of alpha-linolenic acid reached 0.8% of total fatty acids and its production was not increased by adding exogenous oleic acid; alpha-linolenic acid reached 8.7% when exogenous linoleic acid was available.