Publications

• Purification and characterization of (+)dihydroflavonol (3-hydroxyflavanone) 4-reductase from flowers of Dahlia variabilis.

  Fischer D., Stich K., Britsch L., Grisebach H.

  Individual flowers from inflorescences of Dahlia variabilis (cv Scarlet Star) in young developmental stages contained relatively high activity of (+)-dihydroflavonol (DHF) 4-reductase. The DHF reductase was purified from such flowers to apparent homogeneity by a five-step procedure. This included ... >> More

  Individual flowers from inflorescences of Dahlia variabilis (cv Scarlet Star) in young developmental stages contained relatively high activity of (+)-dihydroflavonol (DHF) 4-reductase. The DHF reductase was purified from such flowers to apparent homogeneity by a five-step procedure. This included affinity adsorption on Blue Sepharose and elution of the enzyme with NADP+. By gel filtration and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis it was shown that DHF reductase contains only one polypeptide chain with a Mr of about 41,000. The reductase required NADPH as cofactor and catalyzed transfer of the pro-S hydrogen of NADPH to the substrate. Flavanones and dihydroflavonols (3-hydroxyflavanones) were substrates for DHF reductase with pH optima of about 6.0 for flavanones and of about 6.8 for dihydroflavonols. Flavanones were reduced to the corresponding flavan-4-ols and (+)-dihydroflavonols to flavan-3,4-cis-diols. Apparent Michaelis constants determined for (2S)-naringenin, (2S)-eriodicytol, (+)-dihydrokaempferol, (+)-dihydroquercetin, and NADPH were, respectively, 2.3, 2, 10, 15, and 42 microM. V/Km values were higher for dihydroflavonols than for flavanones. Conversion of dihydromyricetin to leucodelphinidin was also catalyzed by the enzyme at a low rate, whereas flavones and flavonols were not accepted as substrates. DHF reductase was not inhibited by metal chelators. << Less

  Arch Biochem Biophys 264:40-47(1988) [PubMed] [EuropePMC]

• Molecular cloning, substrate specificity of the functionally expressed dihydroflavonol 4-reductases from Malus domestica and Pyrus communis cultivars and the consequences for flavonoid metabolism.

  Fischer T.C., Halbwirth H., Meisel B., Stich K., Forkmann G.

  Treatment with the dioxygenase inhibitor prohexadione-Ca leads to major changes in the flavonoid metabolism of apple (Malus domestica) and pear (Pyrus communis) leaves. Accumulation of unusual 3-deoxyflavonoids is observed, which have been linked to an enhanced resistance toward fire blight. The c ... >> More

  Treatment with the dioxygenase inhibitor prohexadione-Ca leads to major changes in the flavonoid metabolism of apple (Malus domestica) and pear (Pyrus communis) leaves. Accumulation of unusual 3-deoxyflavonoids is observed, which have been linked to an enhanced resistance toward fire blight. The committed step in this pathway is the reduction of flavanones. Crude extracts from leaves are able to perform this reaction. There was previous evidence that DFR enzymes of certain plants possess additional flavanone 4-reductase (FNR) activity. Such an FNR activity of DFR enzymes is proved here by heterologous expression of the enzymes. The heterologously expressed DFR/FNR enzymes of Malus and Pyrus possess distinct differences in substrate specificities despite only minor differences of the amino acid sequences. Kinetic studies showed that dihydroflavonols generally are the preferred substrates. However, with the observed substrate specificities the occurrence of 3-deoxyflavonoids in vivo after application of prohexadione-Ca can be explained. << Less

  Arch. Biochem. Biophys. 412:223-230(2003) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Flavan-3-ol Biosynthesis : The Conversion of (+)-Dihydromyricetin to Its Flavan-3,4-Diol (Leucodelphinidin) and to (+)-Gallocatechin by Reductases Extracted from Tissue Cultures of Ginkgo biloba and Pseudotsuga menziesii.

  Stafford H.A., Lester H.H.

  Extracts of callus or cell suspension cultures from petioles of Ginkgo biloba catalyzed the production of (+)-gallocatechin (2,3-trans-3,5,7,3',4',5'-hexahydroxy-flavan) from (+)-dihydromyricetin (5'-hydroxy-dihydroquercetin) along with the expected 3,4-cis-diol intermediate, leucodelphinidin, in ... >> More

  Extracts of callus or cell suspension cultures from petioles of Ginkgo biloba catalyzed the production of (+)-gallocatechin (2,3-trans-3,5,7,3',4',5'-hexahydroxy-flavan) from (+)-dihydromyricetin (5'-hydroxy-dihydroquercetin) along with the expected 3,4-cis-diol intermediate, leucodelphinidin, in a NADPH-dependent double-step reductase reaction at pH 7.4. The latter diol, isolated from the above incubation mixture, produced (+)-gallocatechin in a NADPH-dependent reaction. Extracts from tissue cultures derived from needles of Pseudotsuga menziesii (Douglas fir) also produced significant amounts of the 3,4-diol from dihydromyricetin. (+)-Dihydromyricetin, purified via paper chromatography from leaves of Leptarrhena pyrolifolia, was reduced by NaBH(4) to the presumed 3,4-trans-diol and acid epimerized to the 3,4-cis-diol. << Less

  Plant Physiol 78:791-794(1985) [PubMed] [EuropePMC]

• Molecular characterization and expression analysis of dihydroflavonol 4-reductase (DFR) gene in Saussurea medusa.

  Li H., Qiu J., Chen F., Lv X., Fu C., Zhao D., Hua X., Zhao Q.

  Dihydroflavonol 4-reductase (DFR), which catalyzes the reduction of dihydroflavonols to leucoanthocyanins, is a key enzyme in the biosynthesis of anthocyanidins, proanthocyanidins, and other flavonoids of importance in plant development and human nutrition. This study isolated a full length cDNA e ... >> More

  Dihydroflavonol 4-reductase (DFR), which catalyzes the reduction of dihydroflavonols to leucoanthocyanins, is a key enzyme in the biosynthesis of anthocyanidins, proanthocyanidins, and other flavonoids of importance in plant development and human nutrition. This study isolated a full length cDNA encoding DFR, designated as SmDFR (GenBank Accession No. EF600682), by screening a cDNA library from a red callus line of Saussurea medusa, which is an endangered, traditional Chinese medicinal plant with high pharmacological value. SmDFR was functionally expressed in yeast (Saccharomyces cerevisiae) to confirm that SmDFR can readily reduce dihydroquercetin (DHQ) and dihydrokampferol (DHK), but it could not reduce dihydromyricetin (DHM). The deduced SmDFR structure shared extensive sequence similarity with previously characterized plant DFRs and phylogenetic analysis showed that it belonged to the plant DFR super-family. SmDFR also possessed flavanone 4-reductase (FNR) activity and can catalyze the conversion of eridictyol to luteoforol. Real-time PCR analysis showed that the expression level of SmDFR was higher in flowers compared with both leaves and roots. This work greatly enhances our knowledge of flavonoid biosynthesis in S. medusa and marks a major advance that could facilitate future genetic modification of S. medusa. << Less

  Mol Biol Rep 39:2991-2999(2012) [PubMed] [EuropePMC]