Functional characterization of a Plagiochasma appendiculatum flavone synthase I showing flavanone 2-hydroxylase activity |
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Authors: | Xiao-Juan Han Yi-Feng WuShuai Gao Hai-Na YuRui-Xue Xu Hong-Xiang Lou Ai-Xia Cheng |
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Affiliation: | Key Laboratory of Chemical Biology of Natural Products, Ministry of Education, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China |
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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. |
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Keywords: | Liverworts Flavone synthase Flavonol synthase 2-Hydroxyflavanone Site-directed mutagenesis |
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