Flavonoid biosynthetic pathway

BURBULIS, I.E., WINKEL-SF1IRLEY, B., Interactions among enzymes of the Arabidopsis flavonoid biosynthetic pathway, Proc. Natl. Acad. Sci. USA, 1999, 96, 12929-12934. 

Katsumoto Y, Fukuchi-Mizutani M, Fukui Y et al (2007) Engineering of the rose flavonoid biosynthetic pathway successfully generated blue-hued flowers accumulating delphinidin. Plant Cell Physiol 48 1589-1600... 

There are many branches to the flavonoid biosynthetic pathways, with the best characterized being those leading to the colored anthocyanins and proanthocyanidins (PAs) and the generally colorless flavones, flavonols, and isoflavonoids. Genes or cDNAs have now been identified for all the core steps leading to anthocyanin, flavone, and flavonol formation, as well as many steps of the isoflavonoid branch, allowing extensive analysis of the encoded enzymes (Table 3.1). In addition, several DNA sequences are available for the modification enzymes that produce the variety of structures known within each class of compound. 

Bradley, J.M. et al.. The maize Lc regulatory gene up-regulates the flavonoid biosynthetic pathway of Petunia. Plant J., 13, 381, 1998. 

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.

Bongue-Bartelsman M, Phillips DA. 1995. Nitrogen stress regulates gene expression of enzymes in the flavonoid biosynthetic pathway of tomato. Plant Physiol Biochem 33 539-546. 

Koes RE, Quattrocchio F, Mol JNM. 1994. The flavonoid biosynthetic pathway in plants Function and evolution. BioEssays 16 123-132. 

Figure 2.1 Simplified scheme of the flavonoid biosynthetic pathway.

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...

While the CHS-CHI-F3H-DFR-AS enzymes form the core flavonoid biosynthetic pathway (Fig. 3.2), every intermediate compound in the pathway can be the subject of complex modifications that include hydroxylations, methylations, esterifications, and decorations with a number of sugar moieties. In addition, many of the core enzymes can utilize various substrates resulting in a pathway that is not linear, but rather a complex grid (Fig. 3.2).2 The diverse forms of flavonoids or anthocyanins that accumulate in any plant under any given condition are the result of a combination of the biosynthetic enzymes being expressed together with their substrate specificity. Over the past few years, the structures of several flavonoid biosynthetic enzymes have been elucidated,1 -20 which opens up unlimited opportunities to understand structure-function relationships and to manipulate the pathway. 

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 -...

Fig. 8. 22 Flavonoid biosynthetic pathways relevant for sented. Modified activities are highlighted in red. DFR di-flower colors. Typical colors resulting Ifom each of the hydroflavonol 4-reductase, ANS anthocyanidin synthase, anthocyanins are indicated by the colored boxes. Other 3GT anthocyanidin 3-O-glucosyltransferase, MT methyl-factors affecting the color like copigments are not repre- transferase...

Flavonoids are a group of secondary plant metabolites. These compounds can be used as antioxidants or antiviral, antibacterial, and anticancer drugs. Many flavonoid biosynthetic pathways are known, and a wide array of flavonoid compounds from 5. cerevisiae are expected to be produced by metabolic engineering in the near future. 

In apple (Malus domestica Borkh.), flavonoid biosynthetic pathway was engineered by introducing maize leaf color (Lc) regulatory gene [73]. Leaf tissue of Lc-transgenic lines had higher levels of anthocyanin idaein (12-fold), flavan 3-ol epicatechin (14-fold), isomeric catechin (41-fold), and dimeric proanthocyanidins (7- to 134-fold). 

Chalcones are the major intermediates of flavonoid biosynthetic pathways they are produced by the condensation of three molecules of malonyl-CoA and a single molecule of 4-coumaryl-CoA. The major precursor malonyl-CoA is derived from citrate, an intermediate product of the TCA cycle. Acetyl-CoA is produced in mitochondria, plastids, peroxisomes, and cytosol via various routes. The cytosolic acetyl-CoA, produced by the multiple subunit enzyme ATP-citrate lyase, is used by acetyl-CoA carboxylase (ACC) to form malonyl-CoA for flavonoid biosynthesis. Another precursor, 4-coumaryl-CoA, is available via the polypropanoid pathway, in which phenylalanine generated via the shikimate and aerogenate pathway is... 

Fig. 54.1 Plant phenylpropanoid and flavonoid biosynthetic pathways representative compounds from each subclass are named...

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