Flavanone synthase

KREUZALER, F., HAHLBROCK, K., Enzymic synthesis of an aromatic ring from acetate units partial purification and some properties of flavanone synthase from cell-suspension cultures of Petroselinum hortense, Eur. J. Biochem., 1975, 56, 205-213. 

Heller, W. and Hahlbrock, K. (1980) Highly purified flavanone synthase from parsley catalyzes the formation of naringenin chalcone. Archives of Biochemistry and Biophysics 200(2), 61 7-619. 

Scheme 1 Schematic representation ofthe biosynthesis pathways of anthocyanins and proanthocyanidins. CHS, chalcone synthase FS, flavanone synthase F3H, flavanone-3-hydroxylase FLS, flavone synthase DFR, dihydroflavonol reductase LAR, leucoanthocyanidin reductase ANS, anthocyanidin synthase ANR, anthocyanidin reductase.

Flavanone synthase catalyzes the formation of narlngenin from p-coumaroyl-CoA and malonyl-CoA. nio key enzyme of flavonoid biosynthesis has been purified from cell suspension cultures of parsley (ref. 5, 6). Recent studies with tulip anthers indicated that the formation of different flavanones can be catalysed with an enzyme preparation from this system (ref. 7, and un-... 

It shlklmate dehydrogenase, 2t phenylalanine ammonia-lyase, 3> cinnamic acid 4-hydroxylase, 4 SAMI caffeate 3-0-methyltransferase, 5t hy-droxyclnnamatet CoA llgase, 6t "flavanone synthase", 7t chalcone-flavanone isomerase, 8t SAMt 3, 4 -dihydroxyflavonoid 3 0-methyltrans-[Pg.236]

Scheme 5. Formation of bisnoryangonin (XVIII) and naringenin (XVI) by flavanone synthase (EI8). HS, Thiol binding sites (after Kreuzaler and Hahlbrock, 1975a).

The immediate product of flavanone synthase (naringenin) in parsley was converted to the isomeric chalcone (XX) by a separate enzyme whose properties were examined by Kreuzaler and Hahlbrock (1975a). A different chal-cone-flavanone isomerase has also been highly purified from soybean seeds (Boland and Wong, 1975). 

Chakon synthase, CHS a plant enzyme (formerly called flavanone synthase) catalysing the synthesis of chalcones from one molecule of the CoA ester of a substituted cinnamic add and 3 molecules of malo-nyl-CoA, a key reaction in flavonoid biosynthesis (see Stilbenes, Hg., and Flavonoid, Hg.). Spedfidty varies with the source of the enzyme, e.g. CHS from Tulipa stamens and Cosmos petals forms naringenin, eriodictyol or homoeriodictyol from 4-coumaroyl-... 

Flavanone synthase see Chalcone synthase. Flavin adenine dinucleotide. FAD, riboflavin... 

Fig. 5 Scheme of the flavonoid pathway leading to synthesis of proanthocyanidins. The enzymes involved in the pathway are shown as follows CHS = chalcone synthase CHI = chalcone isomerase F3H = flavanone-3B-hydroxylase DFR = dihydroflavonol-4-reductase LDOX = leucoanthocynidin dioxygenase LAR = leucoanthocyanidin reductase ANR = anthocyanidin reductase adapted from [27] and [28]... 

Turnbull JJ, Nakajima J, Welford RW, Yamazaki M, Saito K and Schofield CJ. 2004. Mechanistic studies on three 2-oxoglutarate-dependent oxygenases of flavonoid biosynthesis anthocyanidin synthase, flavonol synthase, and flavanone 33-hydroxylase. J Biol Chem 279 1206-1216. 

Figure 6.1 Major branch pathways of flavonoid biosynthesis in Arabidopsis. Branch pathways, enzymes, and end products present in other plants but not Arabidopsis are shown in light gray. Abbreviations cinnamate-4-hydroxylase (C4H), chalcone isomerase (CHI), chalcone synthase (CHS), 4-coumarate CoA-ligase (4CL), dihydroflavonol 4-reductase (DFR), flavanone 3-hydroxylase (F3H), flavonoid 3 or 3 5 hydroxylase (F3 H, F3 5 H), leucoanthocyanidin dioxygenase (LDOX), leucoanthocyanidin reductase (LCR), O-methyltransferase (OMT), phenylalanine ammonia-lyase (PAL), rhamnosyl transferase (RT), and UDP flavonoid glucosyl transferase (UFGT).

PELLETIER, M.K., SHIRLEY, B.W., Analysis of flavanone 3-hydroxylase in Arabidopsis seedlings Coordinate regulation with chalcone synthase and chalcone isomerase, Plant Physiol., 1996, 111, 339-345. 

CL, 4-coumarate CoA ligase CHS, chalcone synthase CHI, chalcone isomerase F3H, flavanone 3-hydroxylase DFR, dihydroflavonol 4-reductase ANS, anthocyanidin synthase FGT, flavonoid 3-O-glucosyltransferase. 

Figure 8.5 Phenylpropanoid biosynthetic pathway. IFS 2-hydroxyisoflavanone synthase F2H flavanone-2-hydroxylase F3 5 H flavnonoid-3 ,5 -hydroxylase...

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. 

Lewinsohn E, Britsch L, Mazur Y, Gressel J (1989) Flavanone glycoside biosynthesis in Citrus chalcone synthase, UDP-glucose flavanone-7-0-glucosy-transferase and -rhamnosyltransferase activities in cell-free extracts. Plant Physiol 91 1321-1328... 

Halbwirth H, Fischer TC, Schlangen K, Rademacher W, Schleifer K, Forkmann G, Stitch K (2006) Screening for inhibitors of 2-oxoglutarate-dependent dioxygenases flavanone 3-hydroxylase and flavonol synthase. Plant Sd 171 194-205... 

Akashi, T. et al.. Molecular cloning and biochemical characterization of a novel cytochrome P450, flavone synthase II, that catalyzes direct conversion of flavanones to flavones. Plant Cell Physiol, 40, 1182, 1999. 

Akashi, T., Aoki, T., and Ayabe, S., Identification of a cytochrome P450 cDNA encoding (25)-flavanone 2-hydroxylase of licorice Glycyrrhiza echinata L. Fabaceae) which represents licodione synthase and flavone synthase II. FEES Lett., 431, 287, 1998. 

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