Plant Tropane Alkaloid Biosynthesis Evolved Independently in the Solanaceae and Erythroxylaceae
Plant tropane alkaloid biosynthesis evolved independently in the Solanaceae and Erythroxylaceae Jan Jirschitzkaa, Gregor W. Schmidta, Michael Reichelta, Bernd Schneiderb, Jonathan Gershenzona, and John Charles D’Auriaa,1 aDepartment of Biochemistry, Max Planck Institute for Chemical Ecology, D-07745 Jena, Germany; and bNMR Research Group, Max Planck Institute for Chemical Ecology, D-07745 Jena, Germany Edited by Jerrold Meinwald, Cornell University, Ithaca, NY, and approved May 4, 2012 (received for review January 11, 2012) The pharmacologically important tropane alkaloids have a scat- Studies of the biosynthesis of tropane alkaloids have been tered distribution among angiosperm families, like many other predominantly performed with members of the Solanaceae and groups of secondary metabolites. To determine whether tropane to a lesser extent with cultivated species of the Erythroxylaceae. alkaloids have evolved repeatedly in different lineages or arise The majority of these studies used in vivo feeding of radiolabeled from an ancestral pathway that has been lost in most lines, we precursors (4–6) to elucidate the outlines of a general tropane investigated the tropinone-reduction step of their biosynthesis. In alkaloid biosynthetic pathway (7, 8). Biosynthesis is initiated species of the Solanaceae, which produce compounds such as from the polyamine putrescine, which is derived from the amino atropine and scopolamine, this reaction is known to be catalyzed acids ornithine or arginine (Fig. S1). Putrescine becomes N- by enzymes of the short-chain dehydrogenase/reductase family. methylated via the action of putrescine methyltransferase in what However, in Erythroxylum coca (Erythroxylaceae), which accumu- is generally considered to be the first committed step in tropane lates cocaine and other tropane alkaloids, no proteins of the short- alkaloid production (9).
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