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Applied and Environmental Microbiology, July 2005, p. 3617-3623, Vol. 71, No. 7
0099-2240/05/$08.00+0 doi:10.1128/AEM.71.7.3617-3623.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.
Department of Chemical and Biological Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260,1 DuPont Central Research and Development, Experimental Station, Wilmington, Delaware 19880,2 Institut für Pharmazeutische Biologie, Philipps-Universität Marburg, Deutschhausstrasse 17A, D-35037 Marburg, Germany3
Received 12 October 2004/ Accepted 25 January 2005
Anthocyanins are red, purple, or blue plant pigments that belong to the family of polyphenolic compounds collectively called flavonoids. Their demonstrated antioxidant properties and economic importance to the dye, fruit, and cut-flower industries have driven intensive research into their metabolic biosynthetic pathways. In order to produce stable, glycosylated anthocyanins from colorless flavanones such as naringenin and eriodictyol, a four-step metabolic pathway was constructed that contained plant genes from heterologous origins: flavanone 3ß-hydroxylase from Malus domestica, dihydroflavonol 4-reductase from Anthurium andraeanum, anthocyanidin synthase (ANS) also from M. domestica, and UDP-glucose:flavonoid 3-O-glucosyltransferase from Petunia hybrida. Using two rounds of PCR, each one of the four genes was first placed under the control of the trc promoter and its own bacterial ribosome-binding site and then cloned sequentially into vector pK184. Escherichia coli cells containing the recombinant plant pathway were able to take up either naringenin or eriodictyol and convert it to the corresponding glycosylated anthocyanin, pelargonidin 3-O-glucoside or cyanidin 3-O-glucoside. The produced anthocyanins were present at low concentrations, while most of the metabolites detected corresponded to their dihydroflavonol precursors, as well as the corresponding flavonols. The presence of side product flavonols is at least partly due to an alternate reaction catalyzed by ANS. This is the first time plant-specific anthocyanins have been produced from a microorganism and opens up the possibility of further production improvement by protein and pathway engineering.
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