Reconstitution of early paclitaxel biosynthetic network.

Paclitaxel is an anticancer therapeutic produced by the yew tree. Over the last two decades, a significant bottleneck in the reconstitution of early paclitaxel biosynthesis has been the propensity of heterologously expressed pathway cytochromes P450, including taxadiene 5α-hydroxylase (T5αH), to form multiple products. Here, we structurally characterize four new products of T5αH, many of which appear to be over-oxidation of the primary mono-oxidized products. By tuning the promoter strength for T5αH expression in Nicotiana plants, we observe decreased levels of these proposed byproducts with a concomitant increase in the accumulation of taxadien-5α-ol, the paclitaxel precursor, by three-fold. This enables the reconstitution of a six step biosynthetic pathway, which we further show may function as a metabolic network. Our result demonstrates that six previously characterized Taxus genes can coordinatively produce key paclitaxel intermediates and serves as a crucial platform for the discovery of the remaining biosynthetic genes. Paclitaxel is an important anticancer drug whose biosynthetic pathway reconstruction is hindered by the propensity of heterologously expressed pathway cytochromes P450, including taxadiene 5α-hydroxylase (T5αH), to form multiple products. Here, the authors tune the promoter strength for T5αH expression in Nicotiana plants to increase the levels of paclitaxel precursor taxadien-5α-ol by three-fold and reconstitute the six step early biosynthetic pathway of paclitaxel. [ABSTRACT FROM AUTHOR]