- Functional characterization of a UDP-glucose:flavonoid 3-O- glucosyltransferase from the seed coat of black soybean (Glycine max (L.) Merr.)
-
The seed coats of black soybean (Glycine max (L.) Merr.) accumulate red (cyanidin-), blue (delphinidin-), purple (petunidin-), and orange (pelargonidin-based) anthocyanins almost exclusively as 3-O-glucosides; however, the responsible enzyme has not been identified. In this study, the full-length cDNA which encodes the enzyme that catalyzes the final step in anthocyanin biosynthesis, namely UDP-glucose:flavonoid 3-O-glucosyltransferase (UGT78K1), was isolated from the seed coat tissue of black soybean using rapid amplification of cDNA ends (RACE). Of the 28 flavonoid substrates tested, the purified recombinant protein glucosylated only anthocyanidins and flavonols, and demonstrated strict 3-OH regiospecificity. Galactose could also be transferred with relatively low activity to the 3-position of cyanidin or delphinidin in vitro. These findings are consistent with previous reports of mainly 3-O-glucosylated and minor amounts of 3-O-galactosylated anthocyanins in the seed coat of black soybean. The recombinant enzyme exhibited pronounced substrate inhibition by cyanidin at 100 μM acceptor concentration. Transfer of UGT78K1 into the Arabidopsis T-DNA mutant (ugt78d2) deficient in anthocyanidin and flavonol 3-O-glucosyltransferase activity, restored the accumulation of anthocyanins and flavonols, suggesting the in vivo function of the enzyme as a flavonoid 3-O-glucosyltransferase. Genomic and phylogenetic analyses suggest the existence of three additional soybean sequences with high similarity to UGT78K1. RT-PCR confirmed the co-expression of one of these genes (Glyma08g07130) with UGT78K1 in the seed coat of black soybean, suggesting possible functional redundancies in anthocyanin biosynthesis in this tissue.
- Kovinich, Nik,Saleem, Ammar,Arnason, John T.,Miki, Brian
-
experimental part
p. 1253 - 1263
(2011/04/22)
-
- 145. Synthesis of 3-Methoxy- and 3-(β-D-Glucopyranosyloxy)flavylium Ions. Influence of the Flavylium Substitution Pattern on the Reactivity of Anthocyanins in Aqueous Solution
-
The synthesis of 3-glycosyloxylated flavylium ions (anthocyanins), in particular of callistephin (4), a natural anthocyanin, is described.The structural transformations in aqueous solution and molecular complexation with chlorogenic acid (7) and caffeine (8) of the synthesized pigments 3 and 4 are investigated and compared to those of the corresponding 3-methoxyflavylium ions 1 and 2 and to those of oenin (5) and malvin (6), two very common natural anthocyanins.The results are discussed in terms of the role played by the glycosyloxy residues in the chemical properties of anthocyanins.Anthocyanin molecular complexation (copigmentation) is quantitatively investigated by UV/VIS spectroscopy and 1H-NMR.In particular, the UV/VIS spectroscopic data are interpreted using a general theoretical treatment, which, e.g., allows to demonstrate the formation of molecular complexes between the colourless forms of an anthocyanin and 8.
- Dangles, Olivier,Elhajji, Hakima
-
p. 1595 - 1610
(2007/10/02)
-