Figure 2.

Glyceollin biosynthesis pathway. The isoflavone daidzein serves as the metabolic precursor for the rapid production of glyceollins. Daidzein is produced through the isoflavonoid branch of the phenylpropanoid pathway starting from L-phenylalanine. Under stress, daidzein is transformed into (6aR, 11aR)-3,9 dihydroxypterocarpan. This molecule is metabolized by CYP93A1 into (-) glycinol. Then, a dimethylallyl group is attached to the glycinol at position 2, which leads to the production of glyceollin II and III, or at position 4, which leads to the production of glyceollin I. These two steps are catalyzed by trihydroxypterocarpan dimethylallyl transferase and glyceollin synthase, respectively.