Chalcone 3-hydroxylase

Fig. 5 Scheme of the flavonoid pathway leading to synthesis of proanthocyanidins. The enzymes involved in the pathway are shown as follows CHS = chalcone synthase CHI = chalcone isomerase F3H = flavanone-3B-hydroxylase DFR = dihydroflavonol-4-reductase LDOX = leucoanthocynidin dioxygenase LAR = leucoanthocyanidin reductase ANR = anthocyanidin reductase adapted from [27] and [28]... 

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.

Figure 6.1 Major branch pathways of flavonoid biosynthesis in Arabidopsis. Branch pathways, enzymes, and end products present in other plants but not Arabidopsis are shown in light gray. Abbreviations cinnamate-4-hydroxylase (C4H), chalcone isomerase (CHI), chalcone synthase (CHS), 4-coumarate CoA-ligase (4CL), dihydroflavonol 4-reductase (DFR), flavanone 3-hydroxylase (F3H), flavonoid 3 or 3 5 hydroxylase (F3 H, F3 5 H), leucoanthocyanidin dioxygenase (LDOX), leucoanthocyanidin reductase (LCR), O-methyltransferase (OMT), phenylalanine ammonia-lyase (PAL), rhamnosyl transferase (RT), and UDP flavonoid glucosyl transferase (UFGT).

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.

PELLETIER, M.K., SHIRLEY, B.W., Analysis of flavanone 3-hydroxylase in Arabidopsis seedlings Coordinate regulation with chalcone synthase and chalcone isomerase, Plant Physiol., 1996, 111, 339-345. 

CL, 4-coumarate CoA ligase CHS, chalcone synthase CHI, chalcone isomerase F3H, flavanone 3-hydroxylase DFR, dihydroflavonol 4-reductase ANS, anthocyanidin synthase FGT, flavonoid 3-O-glucosyltransferase. 

Fig. (1). Schematic view of some branches of phenylpropanoid metabolism. Solid arrows indicate enzymatic reactions with the respective enzyme indicated on the right. PAL, phenylalanine ammonia-lyase C4H, cinnamate 4-hydroxylase 4CL, 4-coumarate CoA ligase CHS, chalcone synthase CF1, chalcone flavavone isomerase F3H, flavanone 3-hydroxylase DFR, dihydroflavonol reductase CHR, chalcone reductase. Broken arrows indicate metabolic branches towards several classes of phenylpropanoids, or several subsequent enzymatic steps. In some cases the enzymes indicated are also involved in other reactions, not shown.

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.

Fig. 1. Simplified diagram of the phenylpropanoid and flavonoid biosynthetic pathways. Enzymes that catalyze the reactions are placed on the left-hand side, and transcription factors on the right-hand side of the arrows. Both transcription factors for which their control over the enzymatic steps has been genetically proven, as well as transcription factors that have been shown to interact with promoters of the structural genes, are shown. PAL Phenylalanine ammonia lyase C4H cinnamate 4-hydroxylase 4CL 4-coumaroyl-coenzyme A ligase CHS chalcone synthase CHI chalcone-flavanone isomerase F3H flavanone 3(3-hydroxylase DFR dihydroflavonol 4-reductase AS anthocyanin synthase UFGT UDP glucose-flavonol glucosyl transferase RT anthocyanin rhamnosyl transferase...

Scheme 1.1 Pathway for the biosynthesis of the major classes of flavonoids. 1, Chalcone synthase 2, chalcone isomerase 3, flavone synthase 4, flavanone 3-hydroxylase 5, flavonol synthase 6, dihydroflavonol reductase 7, anthocyanidin synthase 8, anthocyanidin glucosyltransferase 9, chalcone-ketide reductase 10, chalcone isomerase 11, isoflavone synthase 12, isoflavone 2 -hydroxylase 13, isoflavone reductase 14, pterocarpan synthase 15, pterocarpan 6a-hydroxylase 16, prenyltransferase 17, prenylcyclase.

Chalcone synthase (CHS) and chalcone reductase (CHR) convert 4-coumaro-yl-CoA (15) and 3 mol malonyl-CoA (16) to trihydroxychalcone (a chalcone) (17) via tetrahydroxychalcone (a chalcone) (18). Chalcone isomerase (CHI) converts trihydroxychalcone (a chalcone) (17) into liquiritigenin (7,4/-dihydroxyllavanone, a flavanone) (19). Isoflavone synthase (IFS) converted flavanone (19) to isoflavones (20) such as daidzein (21) and genis-tein (22). Isoflavone 2/-hydroxylase (I2 H) hydroxylated isoflavones (20) to 4/-methoxyisoflavones (23). Isoflavone 2 -hydroxylase (I2 H) hydroxylated 4/-methoxyisoflavones (23) into 2/-hydroxy-4/-methoxyisoflavones (24). Isoflavone reductase (IFR) reduced 2/-hydroxy-4/-methoxyisoflavones (24) to 2/-hydroxy-4/-methoxyisoflavonones (25). Finally, vestitone reductase (VR) and 4/-methoxyisoflavanol dehydrogenase (DMID) cyclized 2/-hydroxy-4/-methoxyisoflavonones (25) to form isoflavonoids (26) such as medicarpin (27) (Fig. 4) [23,24]. 

Fig. 11.1 Simplified diagram of the flavonoid biosynthetic pathway, starting with the general phenylpropanoid metabolism and leading to the main types of flavonoids. Only a few examples are illustrated of the large variety of flavonoids that arise through modification at different positions (not indicated or shown as R). Enzymes catalysing some key reactions are indicated by the following abbreviations PAL, phenylalanine ammonia-lyase CHS, chalcone synthase CHI, chalcone isomerase DFR, dihydroflavonol reductase F3H, flavanone 3-hydroxylase F3 5 H, flavonoid 3 5 -...

Scheme 1 Schematic representation ofthe biosynthesis pathways of anthocyanins and proanthocyanidins. CHS, chalcone synthase FS, flavanone synthase F3H, flavanone-3-hydroxylase FLS, flavone synthase DFR, dihydroflavonol reductase LAR, leucoanthocyanidin reductase ANS, anthocyanidin synthase ANR, anthocyanidin reductase.

CHS, chalcone. synthase CHI, chalcone isomerase IFS+IFD, 2-hydroxyisoflavanone synthase + dehydratase IOMT, Isoflavone 4 -0-methyI transferase FLH, flavone 3-hydroxylase FLS, flavonol synthase... 

Fig, 5.2. Biosynthesis of flavonoids and proanthocyanidins (condensed tannins). Enzymes in bold have been cloned from P. tremuloides and show induction by herbivory (Peters and Constabel, 2002 R. Mellway and C. P. Constabel, unpublished data). Abbreviations are as follows Phe, phenylalanine PAL, phenylalanine ammonia lyase 4CL, 4-coumarate CoA Ligase CHS, chalcone synthase CHI, chalcone isomerase F3H, flavanone 3-hydroxylase FLS, flavonol synthase DFR,... 

The biosynthetic pathway for isoflavonoids in soybean and the relationship of the isoflavonoids to several other classes of phenylpropanoids is presented in Fig. 8.2. Production of /i-coumaryl-CoA from phenylalanine requires phenylalanine ammonia lyase to convert phenylalanine to cinnamate, cinnamic acid hydroxylase to convert cinnamate to /7-coumarate, and coumaraterCoA ligase to convert jt -coumarate to -coumaroyl-CoA. Lignins may be produced from j3-coumaroyl-CoA or from />-coumarate. Chalcone synthase catalyzes the condensation of three molecules of malonyl CoA with p-coumaroyl-CoA to form 4, 2 , 4 , 6 -tetrahydroxychalcone, which is subsequently isomerized in a reaction catalyzed by chalcone isomerase to naringenin, the precursor to genistein, flavones, flavonols, condensed tannins, anthocyanins, and others. 

Alternatively, chalcone reductase (CHR also known as deoxychalcone synthase) together with chalcone synthase and NADPH as a cofactor act in the formation of isoliquiritigenin, which is then isomerized, again by the enzyme chalcone isomerase, to form liquiritigenin, the precursor to daidzein, and the pterocarpan phytoalexins. A type II chalcone isomerase that seems to be found exclusively in the legumes catalyzes this isomerization reaction. Glycitein synthesis is not yet clearly defined, but is likely derived from liquiritigenin via flavonoid 6-hydroxylase, and an unidentified methyltransferase. 

It shlklmate dehydrogenase, 2t phenylalanine ammonia-lyase, 3> cinnamic acid 4-hydroxylase, 4 SAMI caffeate 3-0-methyltransferase, 5t hy-droxyclnnamatet CoA llgase, 6t "flavanone synthase", 7t chalcone-flavanone isomerase, 8t SAMt 3, 4 -dihydroxyflavonoid 3 0-methyltrans-[Pg.236]

Dihydrokaempferol (13) appears to arise by direct hy-droxylation of naringenin (10) at the 3-position, catalyzed by a dioxygenase, flavanone 3-hydroxylase (Grisebach, 1985 Heller and Forkmann, 1988 Stafford, 1991). The enzjmie requires 2-oxoglutarate, Fe ", and ascorbate as cofactors. (2S)-Naringenin [but not the (2/ )-enantiomer] is a substrate for the enzyme. The product formed has been identified as (2/ , 3/ )-dihydroquercetin. Although the intermediacy of a chalcone 2,3-epoxide (19) for the synthesis of dihydroflavonols such as taxifolin (18) has been proposed, this synthesis may occur by hydroxylated intermediates (Fig. 11.11). 

Flavonoids are a diverse family of plant polyphenols and of special interest due to their potential in the treatment of various human diseases. The first attempts to produce flavonoid precursors were accomplished by cloning of the flavanone pathway consisting of cinnamate-4-hydroxylase (CYP73A5) from A. thalima together with 4-coumaroyl CoA ligase (4CL), chalcone synthase (CHS), and chalcone isomerase (CHI) in S. cerevisiae [410], The generated strain was able to convert cinnamic acid to 200 pg naringenin... 

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