Flavonoids flavonoid 3 -hydroxylase

Figure 5.4. Abbreviated scheme for biosynthesis of major flavonoid subclasses, showing the primary enzymes and substrates leading to different subclasses. Bold-faced, uppercase abbreviations refer to enzyme names, whereas substrate names are presented in lowercase letters. PAL, phenylalanine ammonia lyase C4H, cinnamate 4-hydroxylase 4CL, 4-coumarate CoA ligase CHS, chalcone synthase CHI, chalcone isomerase CHR, chalcone reductase IPS, isoflavone synthase F3H, flavonone 3-hydroxylase F3 H, flavonoid 3 -hydroxylase F3 5 H, flavonoid 3 5 -hydroxylase FNSI/II, flavone synthase DFR, dihydroflavonol 4-reductase FLS, flavonol synthase ANS, anthocyanidin synthase LAR, leucoanthocyanidin reductase ANR, anthocyanidin reductase UFGT, UDP-glucose flavonoid 3-O-glucosyltransferase. R3 = H or OH. R5 = H or OH. Glc = glucose. Please refer to text for more information.

Table 6.1 Abbreviations BAN, BANYULS bHLH, basic helix-loop-helix CHS, chalcone synthase CHI, chalcone isomerase DFR, dihydroflavonol reductase F3H, flavonol 3-hydroxylase F3 H, flavonoid 3 -hydroxylase FLS, flavonol synthase icx, increased chalcone synthase expression LDOX, leucoanthocyanidin dioxygenase LCR, leucoanthocyanidin reductase MATE, multidrug and toxic compound extrusion NR, not yet reported tt, transparent testa ttg, transparent testa glabrous the WD40 and WRKY transcription factors are named for conserved amino acid sequences within these proteins. PC = personal communication.

SCHOENBOHM, C., MARTENS, S., EDER, C., FORKMANN, G WEISSHAAR, B., Identification of the Arabidopsis thaliana flavonoid 3 -hydroxylase gene and functional expression of the encoded P450 enzyme, Biol. Chem., 2000,381, 749-753. 

The riocus encodes the enzyme flavonoid 3 -hydroxylase (F3 H) [17, 18], and is an important controller of flux in the anthocyanin pathway in soybean seed coats (Fig. 4.1). F3 H diverts metabolic flux away from biosynthesis of orange (pelargoni-din) and blue (delphinidin) anthocyanins toward the red cyanidin-3-(9-glucoside, which is the main anthocyanin in the seed coats of black soybean [7, 8]. T increases the accumulation of delphidin-3-O-glucoside in black seed coats, even though it is not required for its biosynthesis [19]. Possible mechanisms for this include positive feedback, or the stabilization of the putative anthocyanin biosynthetic metabolon [20] by F3 Fl-derived membrane anchoring (Fig. 4.1). 

Toda K, Yang D, Yamanaka N et al (2002) A single-base deletion in soybean flavonoid 3 -hydroxylase gene is associated with gray pubescence color. Plant Mol Biol 50 187-196... 

Zabala G, Vodkin L (2003) Cloning of the pleiotropic T locus in soybean and two recessive alleles that differentially affect structure and expression of the encoded flavonoid 3 hydroxylase. Genetics 163 295-309... 

HagmannML, HeUerW, GrisebachH (1983) Induction and characterization of a microsomal flavonoid 3 -hydroxylase from parsley cell cultures. Eur J Biochem 134(3) 547-554... 

Brugliera F, Barri-ReweU G, Holton TA, Mason JG (1999) Isolation and characterization of a flavonoid 3 -hydroxylase cDNA clone corresponding to the Htl locus of Petunia hybrida. Plant J 19(4) 441 51... 

Kaltenbach, M. et al., Flavonoid hydroxylase from Catharanthus roseus. cDNA, heterologous expression, enzyme properties and cell-type specific expression in plants. Plant J., 19, 183, 1999. 

Ueyama, Y. et al., Molecular and biochemical characterization of torenia flavonoid 3 -hydroxylase and flavone synthase II and modification of flower color by modulating the expression of these... 

Figure 3-7. Flavonoid biosynthesis (this page and next page). The enzymes involved in this pathway are (a) chalcone synthase (E.C. 2.3.1.73), (b) aureusidin synthase (E.C. 1.21.3.6), (c) chalcone isomerase (E.C. 5.5.1.6), (d) flavanone 3-hydroxylase (E.C. 1.14.11.9), (e) flavone synthase (E.C. 1.14.11.22), (f) flavonoid 3 -hydroxylase (E.C. 1.14.13.21),...

Figure 1.36 Schematic diagram of the stilbene and flavonoid biosynthetic pathway. Enzyme abbreviations SS, stilbene synthase CHS, chalcone synthase CHR, chalcone reductase CHI, chalcone isomerase IFS, isoflavone synthase FNS, flavone synthase F3H, flavanone 3-hydroxylase FLS, flavonol synthase F3 H, flavonoid 3 -hydroxylase DFR, dihydroflavonol 4-reductase LAR, leucoanthocyanidin 4-reductase LDOX, leucocyanidin deoxygenase ANR, anthocyanidin reductase EU, extension units TU, terminal unit.

Bogs J, Ebadi A, McDavid D, Robinson SP. 2006. Identification of the flavonoid hydroxylases from grapevine and their regulation during fruit development. Plant Physiol 140 279-291. 

Latunde-Dada AO, Cabello-Hurtado F, Czittrich N, Didierjean L, Schopfer C, Hertkorn N, Werck-Reichart D, Ebel J. 2001. Flavonoid 6-hydroxylase from soybean (Glycine max L.), a novel plant P-450 monooxygenase. J Biol Chem 276 1685-1688. 

Leonard E, Yan Y, Koffas MA. 2006b. Functional expression of a P450 flavonoid hydroxylase for the biosynthesis of plant-specific hydroxylated flavonols in Escherichia coli. Metab Eng 8 172-181. 

LATUNDI-DADA, A.O., CABELLO-HURTADO, F CZITTRICH, N., DIDIERJEAN, L., SCHOPFER, C., HERTKORN, N., WERCK-REICHHART, D., EBEL, J., Flavonoid 6-hydroxylase from soybean Glycine max L.), a novel plant cytochrome P450 monooxygenase. J. Biol. Chem., 2001,276,1688-1695. 

FORKMANN, G., HELLER, W., GRISEBACH, H Anthocyanin biosynthesis in flowers of Matthiola incana flavanone 3-hydroxylase and flavonoid 3 -hydroxylase. Z. Naturforsch, 1980,35c, 691-695. 

The flavonoid hydroxylases (F3 H, F3 ,5 H) and the phenylpropanoid enzyme cinnamate 4-hydroxylase (C4H) are cytochrome P-450s that are anchored to the cytoplasmic face of the ER.14 F3 H and F3 ,5 H add hydroxyl groups to the 3 and/or 5 of the B ring bringing about chemical and spectral diversity to the flavonoids. Dihydroflavonol 4-reductase (DFR) is the committed step to the production of the precursor of the colored compounds - the leucoanthocyanidins (Fig. 3.2). It is upon the reduction of the 4 keto of the C -ring by DFR (Fig. 3.1) and its further reduction by leucoanthocyanidin dioxygenase/anthocyanidin synthase (LDOX/AS) that the de-localization of the electrons necessary for the formation of the planar flavylium ion is permitted.2... 

Flavanone 3-hydroxylase (F3H) converted naringenin (1) to dihydrokaem-pferol (3-OH-flavanone) (31). Flavonoid 3 -hydroxylase (F3 II) and flavonoid 3 5 -hydroxylasc (r3 5 I I) converted dihydrokaempferol (31) to dihydroflavo-nols (3-OH-flavanones) (32) such as dihydro quercetin (33) and dihydromy-ricetin (34). 

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