This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Flavonoids Biosynthesis → Flavones Biosynthesis|
Expected Taxonomic Range: Viridiplantae
Flavonoids are widely distributed in the plant kingdom. Flavonoids are a highly diverse class of plant secondary metabolites (with about 9000 compounds identified so far [Martens05]) derived from the phenylpropanoid pathway. Based on core structures and chemical modifications flavonoids are classified as chalcones, aurones, flavonols, flavones, flavanones, isoflavones and anthocyanins. Flavonoids serve as pigments (red and purple anthocyanin pigments), act as signals for pollinators and other organisms, participate in plant hormone signaling, facilitate pollen-tube growth, protect plants from UV-B radiation, and function as phytoalexins [Harborne00], [Pietta00], [WinkelShirley01].
Flavone and flavonol-O-glycosides make up one of the largest classes of flavonoid constituents with over 2000 known structures. Although β-D-glucose [Sutter72] and β-L-rhamnopyranose [BarPeled91] are the most frequent O-glycoside conjugates found on flavones and flavonols, the presence of arabinose, xylose, and glucuronic acid has also been reported. The formation of luteolin-7-O-gentiobioside from luteolin 7-O-glucoside catalyzed by a flavonoid 1,6-glucosyltransferase isolated from cultured cells of Catharanthus roseus [Masada09] [Oguchi07] further extends the structural complexity of luteolin glycosides occurring in plants.
Luteolin and glycosidic derivatives thereof belong to the more common flavones found in plants. Several potential functions have been ascribed to luteolin and its glycosides. In humans these compounds have been shown to exhibit anti-oxidant [Hu04a], [Schlupper06], and anti-inflammatory activities [Chen07a].
BarPeled91: Bar-Peled M, Lewinsohn E, Fluhr R, Gressel J (1991). "UDP-rhamnose:flavanone-7-O-glucoside-2''-O-rhamnosyltransferase. Purification and characterization of an enzyme catalyzing the production of bitter compounds in citrus." J Biol Chem 266(31);20953-9. PMID: 1939145
Chen07a: Chen CY, Peng WH, Tsai KD, Hsu SL (2007). "Luteolin suppresses inflammation-associated gene expression by blocking NF-kappaB and AP-1 activation pathway in mouse alveolar macrophages." Life Sci 81(23-24);1602-14. PMID: 17977562
Masada09: Masada S, Terasaka K, Oguchi Y, Okazaki S, Mizushima T, Mizukami H (2009). "Functional and structural characterization of a flavonoid glucoside 1,6-glucosyltransferase from Catharanthus roseus." Plant Cell Physiol 50(8);1401-15. PMID: 19561332
Oguchi07: Oguchi Y, Masada S, Kondo T, Terasaka K, Mizukami H (2007). "Purification and characterization of UDP-glucose : curcumin glucoside 1,6-glucosyltransferase from Catharanthus roseus cell suspension cultures." Plant Cell Physiol 48(11);1635-43. PMID: 17940060
Schlupper06: Schlupper D, Giesa S, Gebhardt R (2006). "Influence of biotransformation of luteolin, luteolin 7-O-glucoside, 3',4'-dihydroxyflavone and apigenin by cultured rat hepatocytes on antioxidative capacity and inhibition of EGF receptor tyrosine kinase activity." Planta Med 72(7);596-603. PMID: 16732514
Sutter72: Sutter A, Ortmann R, Grisebach H (1972). "Purification and properties of an enzyme from cell suspension cultures of parsley catalyzing the transfer of D-glucose from UDP-D-glucose to flavonoids." Biochim Biophys Acta 258(1);71-87. PMID: 5058406
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