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 → Isoflavonoids Biosynthesis|
|Biosynthesis → Secondary Metabolites Biosynthesis → Phytoalexins Biosynthesis → Isoflavonoid Phytoalexins Biosynthesis|
Expected Taxonomic Range: Fabaceae
Note: This is a chimeric pathway, comprising reactions from multiple organisms, and typically will not occur in its entirety in a single organism. The taxa listed here are likely to catalyze only subsets of the reactions depicted in this pathway.
Wighteone and luteone are complex prenylated isoflavones frequently found within the tribe Phaseolae of the legume family [Ingham90]. Their isomers isowighteone and lupiwighteone as well as phaseoluteone have also been isolated from various legume plants [Woodward79] [Stobiecki99]. Monoprenylated isoflavones are both involved in defense mechanisms against pathogens [Abe87] and nod gene induction [Gagnon98].
Prenylated isoflavones such as wighteone and luteone along with the prenylated isoflavanone kievitone have been observed to be more active against pathogens then their non-prenylated analogues (dalbergioidin, genistein, 2'-hydroxygenistein). It has been proposed that the greater lipid-solubility of the prenylated compounds may improve their efficiency [ONeill83]. Interestingly, monoprenylated isoflavones have been characterized as pre-infectional antifungal agent in the genus Lupinus [Harborne76] [Gagnon97] which is different from other phytoalexins which accumulate post-infectional in response to pathogens [Gagnon97].
About This Pathway
The hydroxylation of genistein is carried out by the isoflavone-2'-hydroxylase (I2'H). However, the enzyme(s) isolated from different species have demonstrated various substrate preferences. While I2'H does not hydroxylate genistein in chickpea [Hinderer] [Clemens] the 2'-hydroxylation is carried out in soybean [Kochs86] and licorice [Akashi98]. The intermediate 2'-hydroxygenistein is a branch point leading to the biosynthesis of prenylated isoflavanones such as dalbergioidin and kievitone (kievitone biosynthesis).
Lupinus albus possesses the enzymatic ability to monoprenylate genistein and its 2'-hydroxyl derivative. The enzyme activity is strongly increased upon wounding but the enzyme does not respond to elicitors [Schroeder79]. However, the question of how the mixture of isomers is obtained remains to be investigated.
Superpathways: superpathway of isoflavonoids (via naringenin)
Akashi98: Akashi T, Aoki T, Ayabe S (1998). "CYP81E1, a cytochrome P450 cDNA of licorice (Glycyrrhiza echinata L.), encodes isoflavone 2'-hydroxylase." Biochem Biophys Res Commun 251(1);67-70. PMID: 9790908
Gagnon98: Gagnon H, Ibrahim RK, (1998) "Aldonic Acids: A Novel Family of nod Gene Inducers of Mesorhizobium loti, Rhizobium lupini, and Sinorhizobium meliloti." Molecular Plant-Microbe Interactions (1998), 11(10), 988-998.
Hinderer: Hinderer W, Flentje U, Barz W, (1987) "Microsomal isoflavone 2'- and 3'-hydroxylases from chickpea (Cicer arietinum L.) cell suspensions induced for pterocarpan phytoalexin formation." FEBS Letters, 214(1), 101-106.
Ingham90: Ingham JL, (1990) "Systematic aspects of phytoalexin in formation within tribe Phaseoleae of the Leguminosae (subfamily Papilionoideae)." Biochemical Systematics and Ecology (1990), 18(5), 329-343.
Schroeder79: Schroeder G, Zaehringer U, Heller W, Ebel J, Grisebach H, (1979) "Biosynthesis of antifungal isoflavonoids in Lupinus albus. Enzymatic prenylation of genistein and 2'-hydroxygenistein." Archives of Biochemistry and Biophysics (1979), 194(2), 635-636.
Stobiecki99: Stobiecki M, Malosse C, Kerhoas L, Wojlaszek P, Einhorn J, (1999) "Detection of Isoflavonoids and their Glycosides by Liquid Chromatography/Electrospray Ionization Mass Spectrometry in Root Extracts of Lupin (Lupinus albus)." Phytochem. Anal. (1999) 10, 198-207.
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