Tuesday, July 31, 2007 - 3:30 PM
S105
A study in scarlet: using "color complementation" in E. coli to unravel the biochemical pathway leading to the valuable red ketocarotenoid astaxanthin in the flowers of Adonis aestivalis
Francis X. Cunningham Jr., Department of Cell Biology and Molecular Genetics, University of Maryland, 1109 Microbiology Bldg. & H.J. Patterson Hall, College Park, MD 20742
The red ketocarotenoid astaxanthin (3,3’-dihydroxy-4,4’-diketo-b,b-carotene) has found use as a colorant in foods and cosmetics and as an antioxidant in human nutritional supplements, but is best known for providing an attractive orange-red color to the flesh of wild salmon and the carapace of lobster and other crustaceans. Fish and crustaceans that are raised in captivity require the addition of astaxanthin to their feed in order to acquire the appropriate coloration. The substantial and expanding market for astaxanthin is supplied largely by chemical synthesis. There is considerable interest in the development of a biological production process to provide a less costly source of this valuable pigment. Astaxanthin is synthesized by a number of bacteria, certain green algae, some fungi, and a few species of the flowering plant genus Adonis (Ranunculaceae). We have identified two genes of Adonis aestivalis, the products of which, together, efficiently convert the ubiquitous plant pigment β-carotene into astaxanthin in a simple bacterial system. The route to astaxanthin in Adonis is quite unlike those that lead to astaxanthin in bacteria, algae and fungi. Because the Adonis enzymes are adapted to function in the context of a plant pathway of carotenoid biosynthesis, they may prove particularly useful for the development of an economical, plant-based biological production process for astaxanthin.