Abstracts now available online - Euro Fed Lipid

Characterisation of Primula ∆6-desaturases with distinct substrate
specificities in transgenic yeast and plants
Olga Sayanova, Richard Haslam, Monica Venegas-Caleron and Johnathan Napier.
Crop Performance and Improvement, Rothamsted Research, Harpenden, AL5 2JQ, UK
The biosynthesis of 20-carbon polyunsaturated fatty acids (PUFAs) has been the
subject of intensive research in recent years. PUFAs perform many important functions
in human metabolism and are especially known for their key role in the biosynthesis of
eicosanoids. PUFAs can be classified into the n-6 and n-3 families, derived from the two
essential fatty acids, linoleic acid (LA , 18:2, n-6) and α -linolenic acid (ALA, 18:3, n-3)
respectively. Eicosanoids derived from n-6 PUFAs are functionally distinct to those
derived from n-3 substrates. Eicosanoids derived from n-6 substrates are generally proinflammatory,
whereas the eicosanoids derived from n-3 fatty acids have little or no
inflammatory activity. There is also mounting evidence of the therapeutic role of n-3
PUFAs in human disorders such as Metabolic Syndrome and Cardiovascular disease.
Taking into account the importance of PUFAs in human health, the successful
production of PUFAs (especially the n-3 class) in transgenic oilseeds can provide a
sustainable source of these essential fatty acids.
The “conventional” aerobic pathway which operates in most PUFA-synthesising
eukaryotic organisms, starts with ∆ 6 desaturation of both LA and ALA to yield γlinolenic
(GLA, 18:3, n-6) and stearidonic acid (STA, 18:4, n-3). The first example of the
microsomal ∆ 6 -fatty acid desaturase was cloned from Borago officinalis and orthologs of
the ∆ 6 -desaturase have been identified from many different species, including
mammals, fungi, mosses and plants. All these ∆ 6 -desaturases showed no major
preference for n-6 or n-3 substrates. Recently we have cloned and characterized
several examples of ∆ 6 -fatty acid desaturases from Primula which show strong
specificity towards n-3 substrates when expressed in yeast and transgenic plants. We
also have identified ∆ 6 -desaturase from Primula which displayed a distinct preference
for the n-6 substrate. The identification of fatty acid ∆ 6 -desaturases with n-3/n-6
selectivity has great potential in the heterologous production of PUFAs.