title: Stepwise conversion of flavonoids by engineered dioxygenases and dehydrogenase: Characterization of novel biotransformation products.
abstract: Flavonoids are a large group of plant secondary metabolites that exert various biological and pharmacological effects. In this context, the generation of derivatives is of considerable interest. The introduction of hydroxy groups is of particular relevance, as they are known to be involved in many of the biological interactions and furthermore enable additional modifications, such as glycosylations. Bacterial aryl-hydroxylating dioxygenases (ARHDOs) have proven to be very useful for the conversion of aromatic structures into versatile building blocks for different kinds of derivatizations. Such enzymes have been used with varying success for the oxidation of flavonoids. In order to find better ARHDOs for the hydroxylation of such substrates, we carried out biotransformation trials with a collection of hybrid ARHDOs of different origin, using resting cells of recombinant strains. This identified enzymes able to transform all of the flavonoids examined, typically in yields above 50%. It also showed that moderately reactive substituents of flavonoids, such as hydroxy or amino groups, can lead to spontaneous follow-up reactions with the dienediol structures generated by dioxygenation. A report of flavanone epoxidation, a reaction never before observed to be catalyzed by an ARHDO, is challenged by our results. All ARHDOs examined converted this substrate into a dehydrogenase-transformable dihydrodiol. All dihydrodiols obtained by dioxygenation of the examined flavonoids were successfully re-aromatized into catechols by a bacterial dehydrogenase. These metabolites were usually stable. However, the catechols formed from flavanone and 2'-hydroxy-chalcone, respectively, were interconvertible under mild conditions. Altogether, we isolated and characterized 13 compounds that have not previously been described. The biotransformations reported here give access to novel flavonoid derivatives that may be applied for biological screens as well as for further modification, such as glycodiversification.
authors.affiliation: Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany.
authors.forename: Heike
authors.initials: H
authors.lastname: Overwin
authors.affiliation: Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Departamento de Química & Center for Nanotechnology and Systems Biology & Centro de Biotecnología, Universidad Técnica Federico Santa María, Valparaíso, Chile.
authors.forename: Myriam
authors.initials: M
authors.lastname: González
authors.affiliation: Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Departamento de Química & Center for Nanotechnology and Systems Biology & Centro de Biotecnología, Universidad Técnica Federico Santa María, Valparaíso, Chile.
authors.forename: Valentina
authors.initials: V
authors.lastname: Méndez
authors.affiliation: Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Departamento de Química & Center for Nanotechnology and Systems Biology & Centro de Biotecnología, Universidad Técnica Federico Santa María, Valparaíso, Chile.
authors.forename: Franco
authors.initials: F
authors.lastname: Cárdenas
authors.affiliation: Laboratorio de Microbiología Molecular y Biotecnología Ambiental, Departamento de Química & Center for Nanotechnology and Systems Biology & Centro de Biotecnología, Universidad Técnica Federico Santa María, Valparaíso, Chile.
authors.forename: Michael
authors.initials: M
authors.lastname: Seeger
authors.affiliation: Department of Chemical Biology, Helmholtz Centre for Infection Research, Braunschweig, Germany. Electronic address: bernd.hofer@helmholtz-hzi.de.
authors.forename: Bernd
authors.initials: B
authors.lastname: Hofer
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001711:Biotransformation; D019117:Burkholderia / Q000201:enzymology / Q000235:genetics; D002396:Catechols / Q000737:chemistry / Q000378:metabolism; D049308:Dioxygenases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005419:Flavonoids / Q000737:chemistry* / Q000378:metabolism*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010636:Phenols / Q000737:chemistry / Q000378:metabolism; D015202:Protein Engineering
chemical_list: D001426:Bacterial Proteins; D002396:Catechols; D005419:Flavonoids; D010636:Phenols; D010088:Oxidoreductases; D049308:Dioxygenases
keywords: Chalcone; Dehydrogenase; Diol; Dioxygenase; Flavonoid; Hydroxylation