Figure 1.

Biosynthesis of isoflavonoids from precursor, phenylalanine. The red arrows designate the normal pathway for the production of flavonoids whereas the blue arrows show the pathway for isoflavonoid synthesis. Phenylalanine is converted to coumaryl CoA by the help of 3 enzymes – (1) Phenylalanine ammonia lyase; (2) Cinnamate 4 hydroxylyase; (3) 4-coumarate CoA ligase. Coumaryl CoA gets converted to isoliquiritigenin which is mediated by a novel enzyme known as chalcone reductase (4) in combination with chalcone synthase (4,7). The flavones are formed by the action of chalcone isomerase (5) which is converted to isoflavones by isoflavone synthase (6).