title: Allelic variants from Dahlia variabilis encode flavonoid 3'-hydroxylases with functional differences in chalcone 3-hydroxylase activity.
abstract: In the petals of Dahlia variabilis, hydroxylation of chalcones at position 3 can be detected, except the well-known flavonoid 3'-hydroxylation. Although the reaction is well characterized at the enzymatic level, it remained unclear whether it is catalyzed by a flavonoid 3'-hydroxylase (F3'H, EC1.14.13.21, CYP75B) with broad substrate specificity. Two novel allelic variants of F3'H were cloned from D. variabilis, which differ only in three amino acids within their 508 residues. The corresponding recombinant enzymes show significant differences in their chalcone 3-hydroxylase (CH3H) activity. A substitution of alanine at position 425 with valine enables CH3H activity, whereas the reciprocal substitution leads to a loss of CH3H activity. Interaction of the valine at position 425 with not yet identified structural properties seems to be decisive for chalcone acceptance. This is the first identification of an F3'H which is able to catalyze chalcone 3-hydroxylation to a physiologically relevant extent from any plant species.
authors.affiliation: Institut für Verfahrenstechnik, Umwelttechnik und Technische Biowissenschaften, Technische Universität Wien, Getreidemarkt 9/1665, Vienna, Austria.
authors.forename: Karin
authors.initials: K
authors.lastname: Schlangen
authors.forename: Silvija
authors.initials: S
authors.lastname: Miosic
authors.forename: Heidi
authors.initials: H
authors.lastname: Halbwirth
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D047188:Chalcones / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000235:genetics*; D017931:DNA Primers; D018076:DNA, Complementary; D031944:Dahlia / Q000201:enzymology / Q000235:genetics*; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D047188:Chalcones; D017931:DNA Primers; D018076:DNA, Complementary; D003577:Cytochrome P-450 Enzyme System; C038888:flavonoid 3'-hydroxylase