We are engineering E. coli to produce taxol from an intermediate (10-Deacetylbaccatin III) in the taxol synthesis pathway. We are using a modular approach to link the five necessary genes together onto a single DNA strand so that our design can be easily adapted for next generation taxanes in the future. Each gene in the pathway will be equipped with a T7 promoter of various strengths from a promoter library, fitted to the genes using the ePathOptimize approach for metabolic engineering. The project's end goal is to analyze the activity of produced taxol and evaluate this taxol biosynthesis design's feasibility in industrially relevant conditions. Homology modeling is used to develop protein models for the five necessary genes to determine active site architecture and catalytic functions. These models will then be considered when mutating the genes to produce next generation taxane products.
Why is Taxol important?
Taxol is a cancer drug that works by inhibiting microtubule disassembly during cell division. This helps block the rapid cell division in cancer, but using the opposite mechanism of most anti-mitotic chemicals. Taxol has been shown to be especially effective in blocking ovarian cancer. Please see our human practices page for more information. Rapid, economical, and sustainable production of paclitaxel could save lives!
Serious Issues with Taxol Production
Not surprisingly, there is an ever-increasing demand for taxol. Unfortunately, current production methods for the drug do not provide a long-term, sustainable supply. Taxol is derived from the bark of the Pacific yew tree, Taxus brevifolia, but isolation from its natural source is hindered by the slow growth of the tree and by the low concentration of the drug in the bark. Consequentially, large numbers of yew trees must be harvested for modest returns. Other production methods make use of chemical and semi-chemical synthesis, but the intricate stereoisomerism and multistep pathway of taxol production result in low yield rates (about 2%) and high production costs. Deriving taxol from nature is environmentally unsustainable; chemically synthesizing it is economically unsustainable. Biosynthesis of taxol is the best solution to the shortcomings of the aforementioned production methods. Plant cell fermentation has been shown to synthesize taxol somewhat effectively and requires minimal harvesting of the yew tree. As impressive as plant cell fermentation is, the potential for paclitaxel synthesis in bacteria, an organism much simpler and far more optimized for fermentation, is vastly greater. Duke iGEM’s goal is to optimize the biosynthesis of taxol in E.coli.
Duke iGEM’s goal is to optimize the biosynthesis of taxol in E.coli. We are building on the work of the 2016 Duke iGEM team, which started the design and execution of this biosynthesis project. Their website can be found here. Our project has planned and worked to assemble a 5 gene pathway that, when expressed, can make taxol from a cheap intermediate. Our project has also tested the protein expression of the 5 genes in our pathways.
Bristol-Myers Squibb Company. 2004 Greener Synthetic Pathways Award: Presidential Green Chemistry Challenge. Retrieved from here.
Wall, E. M. & Wani, M.C. (1995). Camptothecin and Taxol: Discovery to Clinic - Thirteenth Bruce F. Cain Memorial Award Lecture. American Association for Cancer Research. Retrieved from here.
More references and information can be found on our human practices page and on the 2016 Duke iGEM page, which contains a lot of background information on this Taxol project.