The biosynthesis and diversity of taxanes: From pathway elucidation, engineering to synthetic biology.

Abstract

Taxanes are diterpenoid natural products found in yew trees (Taxus spp.), and include three anticancer agents paclitaxel, docetaxel, and cabazitaxel. Despite nearly 500 reported taxane compounds, only the biosynthetic pathway of the type one taxane skeleton leading to paclitaxel is close to being fully elucidated. Traditional extraction of these compounds is unsustainable, and chemical synthesis is commercially non-viable. With emerging drug resistance and limited compound diversity, there is an essential need to expand the taxane library and develop sustainable production methods. Here, we propose strategies to elucidate the biosynthetic pathways of various taxane skeletons by identifying and engineering key enzymes such as diterpene synthases, cytochrome P450s (CYP450s), acetyl-transferases and BAHD (BEAT, AHCT, HCBT, and DAT) acyltransferases. We examine the role of metabolon-containing enzyme complexes in optimizing metabolic fluxes and highlight the use of plant chassis such as Nicotiana benthamiana or microbial chassis such as Eschericia coli and Saccharomyces cerevisae for sustainable taxane biosynthesis. Techniques such as compartmentalization and CRISPRi-dCas9-based gene circuits are discussed as routes by which to enhance production efficiency. Additionally, AI-guided directed evolution of CYP450s is proposed as a strategy by which to engineer enzymes with desired properties, facilitating the production of novel and new-to-nature taxane derivatives. The integration of these approaches would facilitate the establishment of a comprehensive taxane library, which in turn could accelerate the discovery of new therapeutic agents.