title: Functional characterization of a Plagiochasma appendiculatum flavone synthase I showing flavanone 2-hydroxylase activity.
abstract: FNS I is a 2-oxoglutarate dependent dioxygenase (2-ODD) found mainly in species of the Apiaceae family. Here, an FNS I cDNA sequence was isolated from the liverwort Plagiochasma appendiculatum (Aytoniaceae) and characterized. The recombinant protein exhibited high FNS I activity catalyzing the conversion of naringenin to apigenin and 2-hydroxynaringenin. The critical residue for flavanone-2-hydroxylation activity was Tyr240, as identified from homology modeling and site-directed mutagenesis. The recombinant protein also showed some flavonol synthase activity, as it can convert dihydrokaempferol to kaempferol. When the Leu311 residue was mutated to Phe, the enzyme's capacity to convert dihydrokaempferol to kaempferol was substantially increased. PaFNS I represents a 2-ODD in which a hydrophobic π-stacking interaction between the key residue and the naringenin A-ring determines 2-hydroxyflavanone formation.
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
authors.forename: Xiao-Juan
authors.initials: XJ
authors.lastname: Han
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
authors.forename: Yi-Feng
authors.initials: YF
authors.lastname: Wu
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Gao
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
authors.forename: Hai-Na
authors.initials: HN
authors.lastname: Yu
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China.
authors.forename: Rui-Xue
authors.initials: RX
authors.lastname: Xu
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China. Electronic address: louhongxiang@sdu.edu.cn.
authors.forename: Hong-Xiang
authors.initials: HX
authors.lastname: Lou
authors.affiliation: Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China. Electronic address: aixiacheng@sdu.edu.cn.
authors.forename: Ai-Xia
authors.initials: AX
authors.lastname: Cheng
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D047310:Apigenin / Q000737:chemistry; D055162:Biocatalysis; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics; D044950:Flavanones / Q000737:chemistry; D035926:Hepatophyta / Q000201:enzymology*; D006899:Mixed Function Oxygenases / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D040681:Structural Homology, Protein
chemical_list: D044950:Flavanones; D010940:Plant Proteins; D047310:Apigenin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C114032:cytochrome P-450 CYP93B1 (Glycyrrhiza echinata); C065998:flavone synthase I; C005273:naringenin
keywords: 2-Hydroxyflavanone; Flavone synthase; Flavonol synthase; Liverworts; Site-directed mutagenesis