中文名称 | 英文名称 | CAS号 | 化学式 | 分子量 |
---|---|---|---|---|
乔松素 | pinocembrin | 480-39-7 | C15H12O4 | 256.258 |
C-糖基黄酮类化合物在植物界中广泛存在,其中许多具有对人类健康有益的作用。它们是一类特殊的类黄酮苷,其中糖基与黄酮骨架C键连接。长期以来,人们一直认为C-糖基黄酮类化合物与O-糖基黄酮类化合物具有不同的生物合成起源。最近在水稻(Oryza sativa)中描述了一种C-葡萄糖转移酶(OsCGT),它接受2-羟基黄酮酮底物和一种脱水酶活性,有选择地将C-葡萄糖基-2-羟基黄酮酮转化为6C-葡萄糖基黄酮。在本研究中,我们提供了体外和体内证据,表明水稻P450 CYP93G2蛋白由Os06g01250编码,是一个功能性的黄酮酮2-羟化酶。CYP93G2与CYP93B亚家族相关,后者由双子叶植物黄酮合成酶II酶组成。在NADPH存在下,重组CYP93G2将柚皮素和二氢黄酮转化为相应的2-羟基黄酮酮。此外,CYP93G2产生2-羟基黄酮酮,在转基因拟南芥(Arabidopsis thaliana)中通过O-糖基化进行修饰。在拟南芥中共表达CYP93G2和OsCGT导致了C-葡萄糖基-2-羟基黄酮酮以二苯甲酮互变异构体形式产生。先前在体外OsCGT反应产物中报告了相同的结构。因此,CYP93G2在植物中将黄酮酮底物转化为由OsCGT进行C-糖基化的2-羟基黄酮酮。此外,在水稻(O. sativa subsp. japonica 'Zhonghua 11')中敲低Os06g01250会优先降低C-糖基黄烯酮、C-糖基槐荚黄酮和C-糖基黄芩酮的积累,但不影响在谷物中经常存在的O-糖苷化物质三糙皮素的水平。综上所述,我们的研究明确将CYP93G2指定为水稻中引导黄酮酮通道到C-糖基黄酮类生物合成的第一个酶。
C-Glycosylflavones are ubiquitous in the plant kingdom, and many of them have beneficial effects on human health. They are a special group of flavonoid glycosides in which the sugars are C-linked to the flavone skeleton. It has been long presumed that C-glycosylflavones have a different biosynthetic origin from O-glycosylflavonoids. In rice (Oryza sativa), a C-glucosyltransferase (OsCGT) that accepts 2-hydroxyflavanone substrates and a dehydratase activity that selectively converts C-glucosyl-2-hydroxyflavanones to 6C-glucosylflavones were recently described. In this study, we provide in vitro and in planta evidence that the rice P450 CYP93G2 protein encoded by Os06g01250 is a functional flavanone 2-hydroxylase. CYP93G2 is related to the CYP93B subfamily, which consists of dicot flavone synthase II enzymes. In the presence of NADPH, recombinant CYP93G2 converts naringenin and eriodictyol to the corresponding 2-hydroxyflavanones. In addition, CYP93G2 generates 2-hydroxyflavanones, which are modified by O-glycosylation in transgenic Arabidopsis (Arabidopsis thaliana). Coexpression of CYP93G2 and OsCGT in Arabidopsis resulted in the production of C-glucosyl-2-hydroxyflavanones in the dibenzoylmethane tautomeric form. The same structure was reported previously for the in vitro OsCGT reaction products. Thus, CYP93G2 generates 2-hydroxyflavanone substrates from flavanones for C-glucosylation by OsCGT in planta. Furthermore, knocking down Os06g01250 in rice (O. sativa subsp. japonica 'Zhonghua 11') preferentially depleted the accumulation of C-glycosylapigenin, C-glycosylluteolin, and C-glycosylchrysoeriol but did not affect the levels of tricin, which is frequently present as O-glycosides in cereals. Taken together, our work conclusively assigned CYP93G2 as the first enzyme that channels flavanones to C-glycosylflavone biosynthesis in rice.
C-糖基黄酮类化合物在植物界中广泛存在,其中许多具有对人类健康有益的作用。它们是一类特殊的类黄酮苷,其中糖基与黄酮骨架C键连接。长期以来,人们一直认为C-糖基黄酮类化合物与O-糖基黄酮类化合物具有不同的生物合成起源。最近在水稻(Oryza sativa)中描述了一种C-葡萄糖转移酶(OsCGT),它接受2-羟基黄酮酮底物和一种脱水酶活性,有选择地将C-葡萄糖基-2-羟基黄酮酮转化为6C-葡萄糖基黄酮。在本研究中,我们提供了体外和体内证据,表明水稻P450 CYP93G2蛋白由Os06g01250编码,是一个功能性的黄酮酮2-羟化酶。CYP93G2与CYP93B亚家族相关,后者由双子叶植物黄酮合成酶II酶组成。在NADPH存在下,重组CYP93G2将柚皮素和二氢黄酮转化为相应的2-羟基黄酮酮。此外,CYP93G2产生2-羟基黄酮酮,在转基因拟南芥(Arabidopsis thaliana)中通过O-糖基化进行修饰。在拟南芥中共表达CYP93G2和OsCGT导致了C-葡萄糖基-2-羟基黄酮酮以二苯甲酮互变异构体形式产生。先前在体外OsCGT反应产物中报告了相同的结构。因此,CYP93G2在植物中将黄酮酮底物转化为由OsCGT进行C-糖基化的2-羟基黄酮酮。此外,在水稻(O. sativa subsp. japonica 'Zhonghua 11')中敲低Os06g01250会优先降低C-糖基黄烯酮、C-糖基槐荚黄酮和C-糖基黄芩酮的积累,但不影响在谷物中经常存在的O-糖苷化物质三糙皮素的水平。综上所述,我们的研究明确将CYP93G2指定为水稻中引导黄酮酮通道到C-糖基黄酮类生物合成的第一个酶。