Flavonol synthase from Citrus unshiu is a bifunctional dioxygenase

Flavonol synthase was classified as a 2-oxoglutarate-dependent dioxygenase converting natural (2 R,3 R)-dihydroflavonols, i.e. dihydrokaempferol, to the corresponding flavonols (kaempferol). Flavonol synthase from Citrus unshiu (Satsuma mandarin), expressed in Escherichia coli and purified to homoge...

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Bibliographic Details
Published in:Phytochemistry (Oxford) 2003-02, Vol.62 (3), p.287-292
Main Authors: Lukačin, Richard, Wellmann, Frank, Britsch, Lothar, Martens, Stefan, Matern, Ulrich
Format: Article
Language:English
Subjects:
Bifunctional dioxygenase
Biological and medical sciences
Chromatography, Thin Layer
Circular Dichroism
Citrus
Citrus - enzymology
Citrus unshiu
Dihydroflavonol hydroxylase
Escherichia coli
Escherichia coli - metabolism
Flavanones
Flavonoid biosynthesis
Flavonoids - biosynthesis
Flavonoids - chemistry
Flavonoids - metabolism
Flavonol synthase
Fundamental and applied biological sciences. Psychology
Kaempferols
Metabolism
Metabolism. Physicochemical requirements
Mixed Function Oxygenases - metabolism
Oxidoreductases - metabolism
Oxygenases - metabolism
Plant physiology and development
Plant Proteins
Quercetin - analogs & derivatives
Quercetin - biosynthesis
Rutaceae
Stereoisomerism
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Summary:Flavonol synthase was classified as a 2-oxoglutarate-dependent dioxygenase converting natural (2 R,3 R)-dihydroflavonols, i.e. dihydrokaempferol, to the corresponding flavonols (kaempferol). Flavonol synthase from Citrus unshiu (Satsuma mandarin), expressed in Escherichia coli and purified to homogeneity, was shown to accept also (2 S)-naringenin as a substrate, producing kaempferol in high yield and assigning sequential flavanone 3β-hydroxylase and flavonol synthase activities to the enzyme. In contrast, dihydrokaempferol was identified as the predominant product from assays performed with the unnatural (2 R)-naringenin as substrate. The product which was not converted any further on repeated incubations was identified by 1H NMR and CD spectroscopies as (−)- trans-dihydrokaempferol. The data demonstrate that Citrus flavonol synthase encompasses an additional non-specific activity trans-hydroxylating the flavanones (2 S)-naringenin as well as the unnatural (2 R)-naringenin at C-3. The recombinant flavonol sythase also catalyzes the 3-hydroxylation of (±) naringenin.
ISSN:0031-9422
1873-3700
DOI:10.1016/S0031-9422(02)00567-8