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Open Access Green as soon as Postprint is submitted to ZB.
Flavonoid 6-Hydroxylase from Soybean (Glycine max L.), a Novel Plant P-450 Monooxygenase.
J. Biol. Chem. 276, 1688-1695 (2001)
Cytochrome P-450-dependent hydroxylases are typical enzymes for the modification of basic flavonoid skeletons. We show in this study that CYP71D9 cDNA, previously isolated from elicitor-induced soybean (Glycine max L.) cells, codes for a protein with a novel hydroxylase activity. When heterologously expressed in yeast, this protein bound various flavonoids with high affinity (1.6 to 52 microm) and showed typical type I absorption spectra. These flavonoids were hydroxylated at position 6 of both resorcinol- and phloroglucinol-based A-rings. Flavonoid 6-hydroxylase (CYP71D9) catalyzed the conversion of flavanones more efficiently than flavones. Isoflavones were hardly hydroxylated. As soybean produces isoflavonoid constituents possessing 6,7-dihydroxy substitution patterns on ring A, the biosynthetic relationship of flavonoid 6-hydroxylase to isoflavonoid biosynthesis was investigated. Recombinant 2-hydroxyisoflavanone synthase (CYP93C1v2) efficiently used 6,7,4'-trihydroxyflavanone as substrate. For its structural identification, the chemically labile reaction product was converted to 6,7,4'-trihydroxyisoflavone by acid treatment. The structures of the final reaction products for both enzymes were confirmed by NMR and mass spectrometry. Our results strongly support the conclusion that, in soybean, the 6-hydroxylation of the A-ring occurs before the 1,2-aryl migration of the flavonoid B-ring during isoflavanone formation. This is the first identification of a flavonoid 6-hydroxylase cDNA from any plant species.
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Publication type
Article: Journal article
Document type
Scientific Article
ISSN (print) / ISBN
0021-9258
e-ISSN
1083-351X
Quellenangaben
Volume: 276 ,
Issue: 3,
Pages: 1688-1695
Publisher
American Society for Biochemistry and Molecular Biology
Non-patent literature
Publications
Reviewing status
Peer reviewed
Institute(s)
Institute of Ecological Chemistry (IOEC)