Ko Jae Hyung, Kim Bong Gyu, Hur Hor-Gil, Lim Yoongho, Ahn Joong-Hoon
Bio/Molecular Informatics Center, Department of Molecular Biotechnology, Konkuk University, Seoul, 143-701, South Korea.
Plant Cell Rep. 2006 Jul;25(7):741-6. doi: 10.1007/s00299-006-0119-4. Epub 2006 Feb 14.
Secondary plant metabolites undergo several modification reactions, including glycosylation. Glycosylation, which is mediated by UDP-glycosyltransferase (UGT), plays a role in the storage of secondary metabolites and in defending plants against stress. In this study, we cloned one of the glycosyltransferases from rice, RUGT-5 resulting in 40-42% sequence homology with UGTs from other plants. RUGT-5 was functionally expressed as a glutathione S-transferase fusion protein in Escherichia coli and was then purified. Eight different flavonoids were used as tentative substrates. HPLC profiling of reaction products displayed at least two peaks. Glycosylation positions were located at the hydroxyl groups at C-3, C-7 or C-4' flavonoid positions. The most efficient substrate was kaempferol, followed by apigenin, genistein and luteolin, in that order. According to in vitro results and the composition of rice flavonoids the in vivo substrate of RUGT-5 was predicted to be kaempferol or apigenin. To our knowledge, this is the first time that the function of a rice UGT has been characterized.
次生植物代谢产物会经历多种修饰反应，包括糖基化。由尿苷二磷酸糖基转移酶（UGT）介导的糖基化在次生代谢产物的储存以及植物抵御胁迫方面发挥作用。在本研究中，我们从水稻中克隆了一种糖基转移酶RUGT - 5，其与其他植物的UGT具有40 - 42%的序列同源性。RUGT - 5在大肠杆菌中作为谷胱甘肽S - 转移酶融合蛋白进行功能表达，随后被纯化。使用了八种不同的黄酮类化合物作为暂定底物。反应产物的高效液相色谱分析显示至少有两个峰。糖基化位置位于黄酮类化合物C - 3、C - 7或C - 4'位的羟基上。最有效的底物是山奈酚，其次依次是芹菜素、染料木黄酮和木犀草素。根据体外实验结果和水稻黄酮类化合物的组成，预测RUGT - 5在体内的底物是山奈酚或芹菜素。据我们所知，这是首次对水稻UGT的功能进行表征。
