Li Jia, Li Changfu, Gou Junbo, Zhang Yansheng
CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of Sciences Wuhan, China.
CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture, Wuhan Botanical Garden, Chinese Academy of SciencesWuhan, China; University of Chinese Academy of SciencesBeijing, China.
Front Plant Sci. 2016 Jun 6;7:793. doi: 10.3389/fpls.2016.00793. eCollection 2016.
Pueraria lobata roots accumulate 3'-, 4'- and 7-O-methylated isoflavones and many of these methylated compounds exhibit various pharmacological activities. Either the 4'- or 7-O-methylation activity has been investigated at molecular levels in several legume species. However, the gene encoding the isoflavone 3'-O-methyltransferase (OMT) has not yet been isolated from any plant species. In this study, we reported the first cDNA encoding the isoflavone 3'-OMT from P. lobata (designated PlOMT4). Heterologous expressions in yeast and Escherichia coli cells showed that the gene product exhibits an enzyme activity to methylate the 3'-hydroxy group of the isoflavone substrate. The transcript abundance of PlOMT4 matches well with its enzymatic product in different organs of P. lobata and in the plant roots in response to methyl jasmonate elicitation. Integration of the biochemical with metabolic and transcript data supported the proposed function of PlOMT4. The identification of PlOMT4 would not only help to understand the isoflavonoid metabolism in P. lobata but also potentially provide an enzyme catalyst for methylating existing drug candidates to improve their hydrophobicity.
野葛根积累3'-、4'-和7-O-甲基化异黄酮，其中许多甲基化化合物具有多种药理活性。在几种豆科植物中，已在分子水平上研究了4'-或7-O-甲基化活性。然而，尚未从任何植物物种中分离出编码异黄酮3'-O-甲基转移酶（OMT）的基因。在本研究中，我们报道了首个来自野葛的编码异黄酮3'-OMT的cDNA（命名为PlOMT4）。在酵母和大肠杆菌细胞中的异源表达表明，该基因产物具有将异黄酮底物的3'-羟基甲基化的酶活性。PlOMT4的转录本丰度与其在野葛不同器官以及植物根中响应茉莉酸甲酯诱导时的酶促产物高度匹配。生化数据与代谢和转录数据的整合支持了PlOMT4的推测功能。PlOMT4的鉴定不仅有助于了解野葛中的异黄酮代谢，还可能为甲基化现有候选药物以改善其疏水性提供一种酶催化剂。
