Identification of a fatty acid Δ11-desaturase from the microalga Thalassiosira pseudonana11The sequence reported in this paper has been submitted to GenBank database under the accession number AY493438.

A set of genomic DNA sequences putatively encoding front-end desaturases were identified by in silico analysis of the draft genome of the marine microalga Thalassiosira pseudonana. Among these candidate genes, an open reading frame named TpdesN was found to be full-length, intronless, and constitutively expressed during cell cultivation. The predicted amino acid sequence of the corresponding protein, TpDESN, exhibited typical features of desaturases involved in the production of polyunsaturated fatty acids (PUFAs) in algae, i.e. a cytochrome b5-like domain at the N-terminus and three conserved histidine-rich motifs in the desaturase domain. Expression of TpDESN in Saccharomyces cerevisiae revealed that this enzyme was not involved in PUFA synthesis, but specifically desaturated palmitic acid 16:0 to 16:1Δ11. To our knowledge, until this report, Δ11-desaturase activity had only been detected in insect cells.