Identification of a Caenorhabditis elegans Δ6-fatty-acid-desaturase by heterologous expression in Saccharomyces cerevisiae

We identified a cDNA expressed sequence tag from an animal (the nematode worm Caenorhabditis elegans) that showed weak similarity to a higher-plant microsomal Delta(6)-desaturase. A full-length cDNA clone was isolated and expressed in the yeast Saccharomyces cerevisiae. This demonstrated that the protein encoded by the C. elegans cDNA was that of a fatty acid Delta(6)-desaturase, as determined by the accumulation of gamma-linolenic acid. The C. elegans Delta(6)-desaturase contained an N-terminal cytochrome b(5) domain, indicating that it had a similar structure to that of the higher-plant Delta(6)-desaturase. The C. elegans Delta(6)-desaturase mapped to cosmid W08D2, a region of chromosome III. This is the first example of a Delta(6)-desaturase isolated from an animal and also the first example of an animal desaturase containing a cytochrome b(5) domain.