Figure 2. Podophyllotoxin biosynthetic pathway. PAL: Phenylalanine ammonia lyase; C4H: Cinnamate 4-hydroxylase; C3H: p-coumarate 3-hydroxylase: 4CL: 4coumarate: CoA ligase; CCOMT: caffeoyl CoA o-methyltransferase; CCR: cinnamoyl CoA reductase; CAD: cinnamyl alcohol dehydrogenase, DP oxidase: Dirigent protein oxidase; PLR: pinoresinol lariciresinol reductase, SDG: Secoisolariciresinol dehydrogenase. Dashed arrows represent multiple unknown reactions.