Flavonoids Biosynthesis

If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.

Locations of Mapped Genes:

 
Synonyms: flavonoid biosynthesis
Superclasses:     Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Flavonoids Biosynthesis → Chalcones Biosynthesis

    Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Flavonoids Biosynthesis
Summary:
Flavonoids are secondary metabolites formed from phenylpropanoid and fatty acid derivatives and have important functions, acting as UV-B protectors [ Ryan01 ], attractors of pollinators and seed dispersers, insect feeding attractors, anti-feedants, signal molecules in legume-rhizobium bacteria interactions [ Peters86 ], and fungicides. Flavonoids have also received a lot of attention due to their effect of human health. In some plant species, flavonoids are required for fertility, but this is not the case in Arabidopsis [ Burbulis96 ].
Biosynthesis is thought to occur in the cytoplasm through enzymes that are associated with the endoplasmatic reticulum membranes [Hrazdina87 ] where the enzymes form a large, macromolecular complex [Burbulis99].
The structure of the major flavonoids in Arabidopsis have recently been described [ Veit99 ]. Under greenhouse conditions, only kaempferol glycosides accumulate in Arabidopsis . With higher UV exposure, quercetin metabolites can be detected as well [ Veit99 ]. Most flavonoids accumulate in the vacuole, the cuticular wax and in the cell wall [ Markham00 ].
Flavonoids constitute a relatively diverse family of aromatic molecules that are derived from Phenylalanine and malonyl-coenzyme A (CoA; via the fatty acidic pathway). [ WinkelShir01 ] There are six major subgroups found in most higher plants: the chalcones, flavones, flavonols, flavandiols, anthocyanins, and condensed tannins (proanthocyanidins); a seventh group, the aurones, are not ubiquitos.
Isoflavonoids are found mostly in legumes but also in a small number of non-legume plants and another specialized form of flavonoids, the phlobaphenes (monomers: 3-deoxyanthocyanins), have been detected in only a few species so far. Stilbenes, closely related to flavonoids, are synthesized by yet another group of unrelated species.