(330e) Drivers of P450 Selectivity in the Taxol Biosynthetic Pathway

Isoprenoids are a large and diverse family of natural products with uses ranging from next-

generation biofuels (isopentenol and farnesene), flavors and fragrances (menthol and

nootkatone), as well as pharmaceuticals (paclitaxel and artemisinin). One of the biggest

contributors to the success of isoprenoids is their diversity. This diversity is generated primarily

through both the initial cyclization step (in which a linear backbone may undergo a complex

rearrangement), and from oxidation steps catalyzed by a family of enzymes known as

cytochrome P450 monooxygenases (P450’s). Paclitaxel (Taxol®), originally derived from the

pacific yew tree, Taxus cuspidata, is a potent chemotherapeutic agent with sales exceeding $3

billion/year. Despite the importance of this molecule and intense study of its synthesis, both

biological and chemical, its biosynthesis and pathways to alternative products remain poorly

understood and industrial production relies on non-recombinant plant-cell culture. Here, we

investigate P450’s as a key driver in the natural diversity of the Taxol-related compounds and

their importance in high-level production of Taxol precursor molecules. We illustrate the

drivers of substrate promiscuity and reaction selectivity on an enzymatic level and then

leverage this understanding to improve the heterologous production of Taxol-precursor

molecules. This work lays a foundation for reliable, scalable production of paclitaxel both

through reconstruction in heterologous hosts and through a deeper understanding, native

plant-cell culture.