The first step in the biosynthesis of cocaine in Erythroxylum coca: the characterization of arginine and ornithine decarboxylases.
Despite the long history of cocaine use among humans and its social and economic significance today, little information is available about the biochemical and molecular aspects of cocaine biosynthesis in coca (Erythroxylum coca) in comparison to what is known about the formation of other pharmacologically-important tropane alkaloids in species of the Solanaceae. In this work, we investigated the site of cocaine biosynthesis in E. coca and the nature of the first step. The two principal tropane alkaloids of E. coca, cocaine and cinnamoyl cocaine, were present in highest concentrations in buds and rolled leaves. These are also the organs in which the rate of alkaloid biosynthesis was the highest based on the incorporation of ¹³CO₂. In contrast, tropane alkaloids in the Solanaceae are biosynthesized in the roots and translocated to the leaves. A collection of EST sequences from a cDNA library made from young E. coca leaves was employed to search for genes encoding the first step in tropane alkaloid biosynthesis. Full-length cDNA clones were identified encoding two candidate enzymes, ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), and the enzymatic activities of the corresponding proteins confirmed by heterologous expression in E. coli and complementation of a yeast mutant. The transcript levels of both ODC and ADC genes were highest in buds and rolled leaves and lower in other organs. The levels of both ornithine and arginine themselves showed a similar pattern, so it was not possible to assign a preferential role in cocaine biosynthesis to one of these proteins.
Department of Biochemistry, Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Teresa
T
Docimo
Michael
M
Reichelt
Bernd
B
Schneider
Marco
M
Kai
Grit
G
Kunert
Jonathan
J
Gershenzon
John C
JC
D'Auria
D000595:Amino Acid Sequence; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism*; D003041:Coca / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D003042:Cocaine / Q000096:biosynthesis* / Q000737:chemistry; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D005816:Genetic Complementation Test; D008954:Models, Biological; D008969:Molecular Sequence Data; D009955:Ornithine Decarboxylase / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D011994:Recombinant Proteins; D002262:Carboxy-Lyases; D009955:Ornithine Decarboxylase; C019722:arginine decarboxylase; D003042:Cocaine