| | 3 | Author
| Nariyuki Ishikura, Zhi-Qing Yang | Requires cookie* | | | Title
| UDP-D-Xylose: Flavonol 3-O-Xylosyltransferase from Young Leaves of Euonymus alatus f. ciliato-dentatus  | | | | Abstract
| From the young leaves of Euonymus alatus f. ciliato-dentatus, a novel enzyme, UDP-D-xylose: flavonol 3-O-xylosyltransferase (F 3 X T), catalyzing the transfer o f D-xylose from UDP-D-xylose to the 3 position o f 3,5,7,4'-tetrahydroxyflavone (kaempferol), was detected and purified about 16-fold by precipitation with am m onium sulfate and DEAE-cellulose CC, by which F 3 X T was separated from two coexisting flavonol O-glucosyltransferases (FGT). Thus, F 3 XT was isolated as a soluble enzyme with a pH optim um o f 7.0 in Tris-HCl buffer. The molecular weight o f F 3 X T , which had an isoelectric point at pH 6.1, was estimated by elution from a column o f Sephadex G-100 to be about 48 kDa. The activity o f F 3 X T was stimulated by 14 mM 2-ME and strongly inhibited by 1 mM C u 2+, 1 mM Z n 2+, and various re agents that react with sulfhydryl groups. Am ong the substrates tested for F 3 X T , kaempferol was the best. The Km values for kaempferol and UDP-xylose were determined to be 0.83 jim and 25 |iM, respectively. F 3 X T mediated the transfer o f xylose exclusively to the 3-hydroxyl group o f kaempferol. Isorhamnetin, quercetin and fisetin also can function as xylosyl acceptor though less efficiently, but neither the 7-O-glucosides nor the 3-O-glucosides o f kaempferol and quercetin were able to accept D-xylose. Dihydroflavonols were not xylosylated. | | | |
Reference
| Z. Naturforsch. 46c, 1003—1010 (1991); received February 28/June 28 1991 | | | |
Published
| 1991 | | | |
Keywords
| Celastraceae, Euonymus, Flavonol, O-Xylosyltransferase, Characterization | | | |
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| default:Reihe_C/46/ZNC-1991-46c-1003.pdf | | | | Identifier
| ZNC-1991-46c-1003 | | | | Volume
| 46 | |
| 4 | Author
| L.M V Jonsson, M.E G Aarsman, J. Bastiaannet, W.E D Onker-K, A.G M Oopm An, A. W. Geräts, Schram | Requires cookie* | | | Title
| Common Identity of UDP-Glucose: Anthocyanidin 3-O-Glucosyltransferase and UDP-Glucose: Flavonol 3-O-Glucosyltransferase in Flowers of Petunia hybrida | | | | Abstract
| In an attempt to distinguish between the U D P -glucose: flavonol 3-O -glucosyltransferase (3G T) and the UD P-glucose:anthocyanidin 3-O-glucosyltransferase in flower buds o f Petunia hybrida, several properties o f these activities were determ ined. The 3-glucosylation o f anthocyanidin had a pH-activity optimum o f 7.2, that o f flavonol pH 9.2 to 9.5. A nthocyanidin 3 G T activity was lowered in the presence o f EDTA or /?-mercaptoethanol, but this was due to an effect on the anthocyanidin substrate. The two 3-glucosylating activities were to a sim ilar extent inhibited by an increasing ionic strength in the enzyme assay and showed an identical iso-electric point (5.2) as determined by chromatofocusing. M olecular weights were identical: 26000, 52000 or 78000 daltons as determined by gel-filtration. Antiserum raised against partially purified 3 G T gave identical immunoprecipitation curves with flavonol 3 G T and anthocyanidin 3G T . Special attention was given to the 3-O-glucosyltransferase in mutants with low levels o f 3 G T activity. These mutants are unable to form significant am ounts o f anthocyanins but contain wild-type amounts o f flavonols. The enzyme o f such mutants had the sam e iso-electric point and identical titration-curves with antiserum as the enzym e from w ildtype plants. 3 G T from w ildtype or mutant plants glucosylated flavonols at higher rates than anthocyanidins. | | | |
Reference
| Z. Naturforsch. 39c, 559 (1984); received February 21 1984 | | | |
Published
| 1984 | | | |
Keywords
| Petunia hybrida, Anthocyanins Flavonoid Biosynthesis, Flavonols, 3-O -G lucosyltransferase | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0559.pdf | | | | Identifier
| ZNC-1984-39c-0559 | | | | Volume
| 39 | |
| 5 | Author
| G. Forkm, P. De Vlaming, R. Spribille, H. Wiering, A. W. Schram | Requires cookie* | | | Title
| Genetic and Biochemical Studies on the Conversion of Dihydroflavonols to Flavonols in Flowers of Petunia hybrida | | | | Abstract
| Soluble enzyme preparations from flower buds of Petunia hybrida catalyzed the conversion of dihydroflavonols to flavonols. Dihydrokaempferol and dihydroquercetin were readily converted to the respective flavonols, whereas dihydromyricetin was a poor substrate. The reaction required 2-oxoglutarate, ascorbate and Fe2+ as cofactors and had a pH optimum at about 6.5. In the presence of the dominant allele FI, high enzyme activity for flavonol formation was found, whereas in enzyme preparations from flower buds of recessive genotypes (fl/fl) only low enzyme activity could be observed. A substantial correlation was found between enzyme activity for flavonol formation and the flavonol content of buds and flowers during development. | | | |
Reference
| Z. Naturforsch. 41c, 179 (1986); received July 27/September 26 1985 | | | |
Published
| 1986 | | | |
Keywords
| birthday Dioxygenase, Flavonoid Biosynthesis, Flavonols, Genetic Control, Petunia hybrida | | | |
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| default:Reihe_C/41/ZNC-1986-41c-0179.pdf | | | | Identifier
| ZNC-1986-41c-0179 | | | | Volume
| 41 | |
| 7 | Author
| K. Stich, T. Eidenberger, F. W. Urst, G. Forkm | Requires cookie* | | | Title
| Flavonol Synthase Activity and the Regulation of Flavonol and Anthocyanin Biosynthesis during Flower Development in Dianthus caryophyllus L. (Carnation) | | | | Abstract
| Flavonol synthase (FLS) was demonstrated in crude extracts from flower buds o f Dianthus caryophyllus (carnation). The enzyme catalyzed the conversion o f dihydrokaempferol and dihydroquercetin to kaempferol and quercetin, respectively. The reaction required 2-oxoglutarate, ferrous ion and ascorbate as co-factors and had a pH optimum at about 7.4. The demonstration o f FLS activity allowed comparative studies on flavonol and anthocyanin biosynthesis during bud and flower developm ent. Besides FLS the flavonoid enzymes chal cone synthase (CHS), flavanone 3-hydroxylase (FH T) and dihydroflavonol 4-reductase (D F R) were measured. D F R is specifically involved in anthocyanin synthesis, while CHS and FHT provide dihydroflavonol, the com m on substrate for both FLS and D F R . Maximum ex pression o f CHS, FHT and FLS activity was already observed in small buds, whereas D FR activity started to increase much later and reached its highest level in opened flowers. A sub stantial correlation was observed between the time courses o f FLS and D F R activity and the accumulation o f flavonols and anthocyanins, respectively. The com petition o f FLS and D F R for dihydroflavonols was found to be largely circumvented by different substrate specificities and by the sequential expression o f the two enzymes. Both flavonols and anthocyanins are obviously not, or only to some extent, subject to degradation. | | | |
Reference
| Z. Naturforsch. 47c, 553 (1992); received February 17/April 21 1992 | | | |
Published
| 1992 | | | |
Keywords
| Anthocyanins, Flavonoid Enzymes, Flavonols, Flower D evelopm ent, Dianthus caryophyllus | | | |
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| default:Reihe_C/47/ZNC-1992-47c-0553.pdf | | | | Identifier
| ZNC-1992-47c-0553 | | | | Volume
| 47 | |
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