<b>Discover the Maze-like Pathway for Glabridin Biosynthesis</b>

Flavonoid diversity arises from modifications of a few precursors by tailored enzymes, yet the complexity of their evolved metabolic networks complicates pathway elucidation and design. Here, we identify and reconstruct the glabridin biosynthetic pathway in yeast, enabling <i>de novo</i> production of this antioxidant flavonoid from the rare plant <i>Glycyrrhiza glabra</i> L.. By analyzing 183 licorice transcriptomes, we discover previously unknown enzymes that modify isoflavan scaffolds. Among 13 theoretical routes, we validate six functional pathways, revealing a ladder-like, multi-route tailoring network that challenges the classical linear view of secondary metabolism. This network features a multi-step “protection–deprotection” mechanism driven by a dynamic methylation–demethylation cycle that regulate intermediate hydrophilicity and enzyme affinity, thereby enabling species-specific glabridin synthesis. Reconstruction of this network in yeast shows that metabolic redundancy and interconnectivity enhance robustness and yield compared to single-route designs. These results establish a biosynthetic paradigm with broad implications for natural product discovery and sustainable biomanufacturing.