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

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 I taxane skeleton leading to paclitaxel is close to being fully elucidated. Traditional extraction of these compounds is unsustainable, and chemical synthesis is commercially nonviable. With emerging drug resistance and limited compound diversity, there is a critical 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), acetyltransferases, and BAHD acyltransferases (BEAT, AHCT, HCBT, and DAT). We examine the roles of metabolon-forming enzyme complexes in optimizing metabolic flux and highlight the use of plant chassis such as Nicotiana benthamiana or microbial chassis such as Escherichia coli and Saccharomyces cerevisiae for sustainable taxane biosynthesis. Techniques such as compartmentalization and CRISPRi-dCas9-based gene circuits are discussed as means to enhance production efficiency. Additionally, artificial intelligence (AI)-guided directed evolution of CYP450s is proposed as a strategy to engineer enzymes with desired properties, facilitating the production of novel and new-to-nature taxane derivatives. The integration of these approaches would support the development of a comprehensive taxane library, which could accelerate the discovery of new therapeutic agents.