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Functional Characterization of a New Tea (Camellia sinensis) Flavonoid Glycosyltransferase
journal contribution
posted on 2017-02-21, 00:00 authored by Xianqian Zhao, Peiqiang Wang, Mingzhuo Li, Yeru Wang, Xiaolan Jiang, Lilan Cui, Yumei Qian, Juhua Zhuang, Liping Gao, Tao XiaTea
(Camellia sinensis) is an important commercial
crop, in which the high content of flavonoids provides health benefits.
A flavonoid glycosyltransferase (CsUGT73A20), belonging to cluster
IIIa, was isolated from tea plant. The recombinant CsUGT73A20 in Escherichia coli exhibited a broad substrate tolerance toward
multiple flavonoids. Among them, kaempferol was the optimal substrate
compared to quercetin, myricetin, naringenin, apigenin, and kaempferide.
However, no product was detected when UDP-galactose was used as the
sugar donor. The reaction assay indicated that rCsUGT73A20 performed
multisite glycosidation toward flavonol compounds, mainly forming
3-O-glucoside and 7-O-glucoside
in vitro. The biochemical characterization analysis of CsUGT73A20
showed more K7G product accumulated at pH 8.0, but K3G was the main
product at pH 9.0. Kinetic analysis demonstrated that high pH repressed
the glycosylation reaction at the 7-OH site in vitro. Besides, the
content of five flavonol-glucosides was increased in CsUGT73A20-overexpressing
tobaccos (Nicotiana tabacum).