The chemical logic of plant natural product biosynthesis

Abstract

Understanding the logic of plant natural product biosynthesis is important for three reasons: it guides the search for new natural products and pathways, illuminates the function of existing pathways in the context of host biology, and builds an enabling 'parts list' for plant and microbial metabolic engineering. In this review, we highlight the chemical themes that underlie a broad range of plant pathways, dividing pathways into two parts: scaffold-generating steps that draw on a limited set of chemistries, and tailoring reactions that produce a wide range of end products from a small number of common scaffolds.

Figure 1.

Key chemical reactions in plant natural product biosynthesis. (a) Common scaffold-generating enzymatic steps are highlighted in the left panel, and (b) Common tailoring themes are highlighted in the right panel.

Figure 2.

Diversity in plant natural products can be established by two general chemical strategies. Examples shown illustrate these two strategies. (a) Common scaffold-generating chemical reactions generate diversity by utilizing closely related, but distinct substrates. (b) Key scaffold intermediates generate diversity by differential tailoring reactions. Multiple arrows indicate multiple chemical transformations.

Figure 3.

Closely related oxidations and resulting skeletal rearrangements in (a) cruciferous phytoalexin biosynthesis and (b) coumaryl-CoA tailoring. Dotted arrows indicate predicted biosynthetic steps.

Figure 4.

Combinations of tailoring chemistries create diverse families of plant natural products. (a) Side chain tailoring of cholesterol scaffold leads to a range of steroidal saponins. (b) Tailoring of daidzein scaffold expands family of isoflavonoids.