Extreme metabolic engineering: microbially-derived artemisinin to combat malaria in the developing world
Amyris Inc., USA
Utilizing the tools of synthetic biology and metabolic engineering, including rapid strain engineering technologies, transcriptomics, proteomics, metabolomics, and high-throughput screening, for the synthesis of socially and economically valuable renewable products.
Website: Amyris Inc.
There are estimated to be over 200 million clinical episodes of malaria annually, caused by the Plasmodium parasite, with over 700,000 deaths. The World Health Organization recommends the use of Artemisinin-based Combination Therapies (ACTs) for the treatment of uncomplicated P. falciparum malaria, but the supply and price of artemisinin (extracted from the plant Artemisia annua) have fluctuated greatly. An additional semi-synthetic source of artemisinin would be advantageous to stabilize the price and availability of ACTs. To this end, we have engineered both Escherichia coli and Saccharomyces cerevisiae (yeast) to produce the artemisinin hydrocarbon precursor amorpha-4,11-diene, and further engineered yeast to produce artemisinic acid. Artemisinic acid is the feedstock for chemical conversion to artemisinin.
Initial engineering of yeast involved limited upregulation of the mevalonate pathway and expression of A. annua enzymes responsible for production of the artemisinin hydrocarbon precursor, amorphadiene, and its oxidation to artemisinic acid1. However, a significant increase in production was required for economic viability, necessitating use of the tools of synthetic biology to re-engineer a strain overexpressing the entire mevalonate pathway. Generation of strains capable of producing 40 g l-1 amorphadiene2 and subsequent efficient oxidation to artemisinic acid will be described. Final production levels of artemisinic acid achieved the goal of generating a microbial strain capable of integration into a process for the semi-synthetic production of artemisinin.
1. Ro DK, Paradise EM, Ouellet M, Fisher KJ, Newman KL, Ndungu JM, Ho KA, Eachus RA, Ham TS et al. 2006. Production of the antimalarial drug precursor artemisinic acid in engineered yeast. Nature 440: 940–943.
2. Westfall PJ, Pitera DJ, Lenihan JR, Eng D, Woolard FX, Regentin R, Horning T, Tsuruta H, Melis DJ, Owens A et al. 2012. Production of amorphadiene in yeast, and its conversion to dihydroartemisinic acid, precursor to the antimalarial agent artemisinin. Proceedings of the National Academy of Sciences, USA 109: E111–E118 (Jan 17, 2012).
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