Ring Formation:** -**Identification of Taxane Oxetanase 1 (TOT1):** -Yan and coworkers identified a bifunctional cytochrome P450 enzyme, named taxane oxetanase 1 (TOT1), which plays a crucial role in forming the oxetane ring-a distinctive and biologically important moiety of paclitaxel. -By transiently expressing genes from the CYP725A subfamily in *Nicotiana benthamiana* and using chemically synthesized taxadiene hexa-acetate as a substrate, they demonstrated that TOT1 catalyzes the oxidative rearrangement of the double bond to form the oxetane ring, producing 1-dehydroxybaccatin IV and baccatin I. -Further validation was achieved by expressing TOT1 in insect cells to avoid interference from endogenous P450s in tobacco and through knockdown experiments in *Taxus* cells, confirming TOT1's role in oxetane ring formation.