Collective biosynthesis of plant spirooxindole alkaloids through enzyme discovery and engineering

Collective synthesis is a well-established strategy to produce natural product collections from common intermediates. Extending this concept to enzymatic systems, collective biosynthesis offers a sustainable approach to diverse molecular collections but faces distinct challenges, including incomplete pathway knowledge and narrow substrate specificity of biosynthetic enzymes. Here, we overcome these limitations through enzyme discovery and protein engineering to achieve collective biosynthesis of spirooxindole alkaloids, an important class of natural products with diverse biological activities. We identified two key enzymes that catalyze enzymatic epimerization, working sequentially with a previously discovered cytochrome P450 enzyme to fully elucidate the biosynthetic pathway of pentacyclic spirooxindole alkaloids. Structure-guided engineering expanded substrate scope, enabling collective biosynthesis of 12 tetracyclic and pentacyclic spirooxindole natural products. We also generated new-to-nature fluorinated and deuterated derivatives through precursor-directed biosynthesis. This work provides crucial insights into plant spirooxindole alkaloid biosynthesis while establishing a powerful approach for sustainable production of complex natural products.