Identification of a novel flavonoid glycoside sulfotransferase in Arabidopsis thaliana
作者:T. Hashiguchi、Y. Sakakibara、T. Shimohira、K. Kurogi、M. Yamasaki、K. Nishiyama、R. Akashi、M.-C. Liu、M. Suiko
DOI:10.1093/jb/mvt102
日期:2014.2.1
The discovery of sulfated flavonoids in plants suggests that sulfation may play a regulatory role in the physiological functions of flavonoids. Sulfation of flavonoids is mediated by cytosolic sulfotransferases (SULTs), which utilize 3′-phosphoadenosine 5′-phosphosulfate (PAPS) as the sulfate donor. A novel SULT from Arabidopsis thaliana, designated AtSULT202B7 (AGI code: At1g13420), was cloned and expressed in Escherichia coli. Using various compounds as potential substrates, we demonstrated, for the first time, that AtSULT202B7 displayed sulfating activity specific for flavonoids. Intriguingly, the recombinant enzyme preferred flavonoid glycosides (e.g. kaempferol-3-glucoside and quercetin-3-glucoside) rather than their aglycone counterparts. Among a series of hydroxyflavones tested, AtSULT202B7 showed the enzymatic activity only for 7-hydroxyflavone. pH-dependency study showed that the optimum pH was relatively low (pH 5.5) compared with those (pH 6.0–8.5) previously reported for other isoforms. Based on the comparison of high performance (pressure) liquid chromatography (HPLC) retention times between sulfated kaempferol and the deglycosylated product of sulfated kaempferol-3-glucoside, the sulfation site in sulfated kaempferol-3-glucoside appeared to be the hydroxyl group of the flavonoid skeleton. In addition, by using direct infusion mass spectrometry, it was found that the sulfated product had one sulfonate group within the molecule. These results indicated that AtSULT202B7 functions as a flavonoid glycoside 7-sulfotransferase.
植物中硫酸盐黄酮类化合物的发现表明硫酸化可能在黄酮类化合物的生理功能中发挥调节作用。黄酮类化合物的硫酸化是由细胞质硫酸转移酶(SULTs)介导的,它们利用3'-磷酸腺苷5'-磷酸硫酸盐(PAPS)作为硫酸供体。从拟南芥中克隆并表达了一种新的SULT,命名为AtSULT202B7(AGI代码:At1g13420),在大肠杆菌中表达。使用各种化合物作为潜在底物,我们首次证明了AtSULT202B7显示出对黄酮类化合物特异的硫酸化活性。有趣的是,重组酶更倾向于黄酮苷(如山柰酚-3-葡萄糖苷和槲皮素-3-葡萄糖苷)而不是它们的苷元形式。在一系列羟基黄酮中,AtSULT202B7仅对7-羟基黄酮表现出酶活性。pH依赖性研究显示,其最佳pH相对较低(pH 5.5),与先前报道的其他同工酶(pH 6.0–8.5)相比。基于高效液相色谱(HPLC)保留时间在硫酸化山柰酚和硫酸化山柰酚-3-葡萄糖苷的去糖基化产物之间的比较,硫酸化山柰酚-3-葡萄糖苷中的硫酸化位点似乎是黄酮骨架上的羟基。此外,通过直接注入质谱法,发现硫酸化产物分子内含有一个磺酸基团。这些结果表明AtSULT202B7是一种黄酮苷7-硫酸转移酶。