Projects per year
Abstract
Flavonoids normally accumulate in plants as O-glycosylated derivatives, but several species, including major cereal crops, predominantly synthesize flavone-C-glycosides, which are stable to hydrolysis and are biologically active both in planta and as dietary components. An enzyme (OsCGT) catalyzing the UDP-glucosedependent C-glucosylation of 2-hydroxyflavanone precursors of flavonoids has been identified and cloned from rice (Oryza sativa ssp. indica), with a similar protein characterized in wheat (Triticum aestivum L.). OsCGT is a 49-kDa family 1 glycosyltransferase related to known O-glucosyltransferases. The recombinant enzyme C-glucosylated 2-hydroxyflavanones but had negligible O-glucosyltransferase activity with flavonoid acceptors. Enzyme chemistry studies suggested that OsCGT preferentially C-glucosylated the dibenzoylmethane tautomers formed in equilibrium with 2-hydroxyflavanones. The resulting 2-hydroxyflavanone-C-glucosides were unstable and spontaneously dehydrated in vitro to yield a mixture of 6C-and 8C-glucosyl derivatives of the respective flavones. In contrast, in planta, only the respective 6C-glucosides accumulated. Consistent with this selectivity in glycosylation product, a dehydratase activity that preferentially converted 2-hydroxyflavanone-C-glucosides to the corresponding flavone-6C-glucosides was identified in both rice and wheat. Our results demonstrate that cereal crops synthesize C-glucosylated flavones through the concerted action of a CGT and dehydratase acting on activated 2-hydroxyflavanones, as an alternative means of generating flavonoid metabolites.
Original language | English |
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Pages (from-to) | 17926-17934 |
Number of pages | 9 |
Journal | Journal of Biological Chemistry |
Volume | 284 |
Issue number | 27 |
DOIs | |
Publication status | Published - 3 Jul 2009 |
Keywords
- ANTIBIOTIC URDAMYCIN
- SECONDARY METABOLISM
- ARABIDOPSIS-THALIANA
- IN-VITRO
- BIOSYNTHESIS
- IDENTIFICATION
- GLYCOSYLTRANSFERASE
- RICE
- GLUCOSYLTRANSFERASE
- GLYCOSIDES
Projects
- 1 Finished
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CGT: The biochemistry of flavone C-glycosides in Cereals
BBSRC (BIOTECHNOLOGY AND BIOLOGICAL SCIENCES RESEARCH COUNCIL)
1/10/10 → 31/03/11
Project: Research project (funded) › Research