Flavone synthase I

Martens S, Forkmann G, Matern U, Lukacin R (2001) Cloning of parsley flavone synthase I. Phytochemistry 58 43-46... 

Yun CS, Yamamoto T, Nozawa A, Tozawa Y (2008) Expression of parsley flavone synthase I establishes the flavone biosynthetic pathway in Arabidopsis thaliana. Biosci Biotechnol Biochem 72(4) 968-973... 

Lukacin R, Matern U, Junghanns KT, Heskamp ML, Britsch L, Forkmann G, Martens S. 2001. Purification and antigenicity of flavones synthase I from irradiated parsley cells. Arch Biochem Biophys 393 177-183. 

BRITSCH, L., Purification and characterization of flavone synthase I, a 2-oxoglutarate-dependent desaturase. Arch Biochem. Biophys., 1990,282,152-160. 

Tetrahydroxychalcone (18) was converted to naringenin (1) by chalcone iso-merase (CHI), and then to flavones (29) by flavone synthase I (FSI) and flavone synthase II (FSII), respectively (Fig. 6). 

Flavone synthase (FNS EC 1.14.11.22) introduces a double bond between C2 and C3 of a flavanone to produce the corresponding flavone. This activity was initially identified in parsley cell suspension cultures and subsequently shown to be encoded by a 2-oxoglutarate-dependent dioxygenase [67, 78, 79], This enzyme, now known as FNS-I, appears to have very limited distribution. To date, it has only been identified in the Apiaceae family (Umbellifers). The more widely occurring FNS-II (CYP93B) was initially identified from snapdragon (Antirrhinum majus) flowers [80] and was subsequently shown to be a P450 enzyme. FNS-I, FNS-II, and the various roles flavones play in plant species have recently been reviewed by Martens and Mithofer [81], Subsequent to this review, Yu et al. [82] demonstrated that the characteristic lack of natural accumulation of flavones in Brassicaceae could not be overcome in A. thaliana even by overexpression of recombinant parsley FNS-I. 

AKASHI, T., FUKUSHI-MIZUTANI, M., AOKI, T UEYAMA, Y., YUNEKURA-SAKAKIBARA, K., TANAKA, Y., KUSUMI, T., AYABE, S.-I., Me ocular cloning and biochemical characterization of a novel cytochrome P450 flavone synthase that catalyzes direct conversion of flavanones to flavones. Plant Cell Physiol., 1999,40,1182-1186. 

AKASHI, T AOKI, T., AYABE, S.-I., Identification of a cytochrome P450 cDNA encoding (2flavone synthase II. FEBS Lett., 1998, 431,287-290. 

Fig. 6.8 Common polyketide pathway leading to flavonoids (CHS = chalcone synthase) and to the stilbene resveratiol (STS = stilbene synthase). CHI = chalcone isomerase FNS I = flavone synthase 1 FNS II = flavone synthase 11 FHT = flavanone 3-hydroxylase FLS = flavonol synthase DFR = dihydroflavonol 4-reductase ANS = anthocyanidin synthase (abbreviations of enzymes according to McAidle et al. 2006)...

Garcia-Mediavilla V, Crespo I, Collado PS, Esteller A, Sanchez-Campos S, Tunon MJ, Gonzalez-Gallego J. 2007. The anti-inflammatory flavones quercetin and kaempferol cause inhibition of inducible nitric oxide synthase, cyclooxygenase-2 and reactive... 

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. 

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