Team:St Andrews/Omega-3-synthesis

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Omega-3 fatty acid synthesis

ω-3 Fatty acids are an essential component of our diet and are para-mount to maintaining human health. Our team is recreating this synthetic pathway in E. coli, using genes from the cyanobacteria Synechocystis and the trypanosomatid Leishmania major. Combining the DNA code for elongase and desaturase enzymes, we can convert the plain fatty acid of E. coli into highly valuable ω-3 fatty acids.



Project Description


  • Synechocystis sp.


  • Trypanosome cruzi


  • Leishmania major

Omega-3 fatty acids are an essential part of the human diet (reference) . Human beings, and all larger organisms cannot synthesize ω-3 fatty acids as they lack a Δ15 desaturase to create a double bond at the correct location. Certain microrganisms, such as microalgae and cyanobacteria, do contain this desaturase and can thus directly synthesize ω-3 fatty acids (Arts et al, 2009). Their anabolic product can then enter the food chain – algae are eaten by fish, and seafood is the main source of ω-3 for humans (Tonon et al, 2002).

However, overfishing is a serious problem in the world’s oceans already, and the human population is estimated to rise to a up to NUMBER (reference). Additionally, global warming will cause a further reduction in the availability of ω-3 (Arts et al, 2009): at higher temperatures, microalgae produce less ω-3 desaturated fatty acids. Desaturated carbon chains cause a lower melting temperature in the membrane, which the microorganism wants to avoid by using more saturated fatty acids in their membranes (Garwin, Cronan, 1980) . Thus, the combination of declining fish stock and a decrease in overall ω-3 fatty acids is making the continuation of supply for human nutrition a relevant issue.

Harvesting algae directly is costly and ineffective (Borowitzka, 1997), so there is much potential in expressing a metabolic pathway for ω-3 fatty acid synthesis in E. coli, which is cheaper and more accessible.


Synthesizing the pathway


  • Diagram showing the elongation and desaturation enzymes necessary to convert an 18,1 fatty acid, which E. coli synthesizes, into an poly-unsaturated fatty acid.

    modified from Livore et al, 2006

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The genes for Δ12, Δ15 (ω6) and Δ6 were obtained from Synechocystis sp., a cyanobacteria. The trypanosomatid Leishmania major provided the DNA for the Elo 6 gene. Additionally, we used Trypanosome cruzi as a secondary source of Δ12.

Please see the Lab Book.


Biobricks


References

M. Arts, M. Brett, M. Kainz (Eds.), Lipids in Aquatic Ecosystems. Springer: 2009.

J. L. Garwin, J. E. Cronan Jr, Thermal modulation of fatty acid synthesis in Escherichia coli does not involve de novo enzyme synthesis. J Bacteriol. 1980 March; 141(3): 1457–1459.

V. Livore, K. Tripodi, A. Utarro, Elongation of polyunsaturated fatty acids in trypanosomatids. FEBS Journal, 274 (2007): 264–274. doi: 10.1111/j.1742-4658.2006.05581.x

T. Tonon, D. Harvey, T. Larson, I. Graham, Long chain polyunsaturated fatty acid production and partitioning to triacylglycerols in four microalgae. Phytochemistry, Volume 61, Issue 1, September 2002, Pages 15-24, ISSN 0031-9422, 10.1016/S0031-9422(02)00201-7.

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University of St Andrews, 2012.

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This iGEM team has been funded by the MSD Scottish Life Sciences Fund. The opinions expressed by this iGEM team are those of the team members and do not necessarily represent those of Merck Sharp & Dohme Limited, nor its Affiliates.