Cyanogenic glucosides are amino acid derived natural products widely distributed in the plant kingdom. Among the more than 3.000 plant species known to contain cyanogenic glucosides are important crop plants like sorghum, barley, cassava, clover, flax, lotus and almonds. The biosynthetic pathway is catalyzed by two membrane bound cytochrome P450s and a soluble UDPG-glucosyltransferase and is highly channelled. This provides a mean to secure “conveyor belt” synthesis of the cyanogenic glucoside and retains the toxic and labile intermediates in a microenvironment preventing their diffusion into the cytosol. Plants producing cyanogenic glucosides, also contain -glycosidases that upon cellular disruption of the plant tissue catalyze their conversion into keto compounds and hydrogen cyanide. This binary system - two sets of components which separately are chemically inert – provides the plants with an immediate chemical defence response to herbivores and pests causing tissue damage.
Transfer of the entire pathway for synthesis of the cyanogenic glucoside dhurrin from sorghum to Arabidopsis using genetic engineering resulted in transgenic plants containing high amounts of dhurrin and demonstrated that plants possess immanent routes for transport and storage of classes of natural products that they would normally not produce or encounter. The mechanisms controlling metabolon formation are studied by molecular modeling and by assembly of the metabolons into synthetic nano discs possessing the characteristics of a soluble protein (collaboration with the Sligar laboratory in Urbana). This opens new opportunities to elucidate how plants based on a limited number of enzymes by combinatorial biochemistry master to synthesize a vast number of different natural products and may enable the design of plants that serve as highly effective “green” factories for synthesis of complex bioactive compounds and valuable fine chemicals.