Rational Engineering of the Dxp Pathway for Overproduction of Isoprenoids in Bacteria

Isoprenoids are a family of natural products (>55,000 examples identified), including many high-value compounds that can be used as pharmaceuticals, nutraceuticals and fragrances. Isoprenoids are naturally synthesized via two pathways, mevalonate pathway and deoxyxylulose phosphate (DXP) pathway. We are interested in exploiting the DXP pathway for overproduction of isoprenoids, because this pathway is more redox balanced and more efficient in terms of pathway yield. To rationally engineer the DXP pathway for isoprenoid overproduction in Escherichia coli and Bacillus subtilis, we have in this study developed a series of methods, which can reliably quantify gene transcription, enzyme solubility and metabolic intermediates in the pathway. For the first time, we have found that one phosphorylated intermediate of the DXP pathway (MEC) could be actively effluxed by the cell, diverting a large portion of carbon flux away from microbial isoprenoid synthesis. The methods developed and the rate-limiting step identified in this study, should be very useful in future practice of using the DXP pathway for high level production of valuable isoprenoids in bacteria.