Abstract
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.
Highlights
Pueraria lobata (P. lobata) is a leguminous plant with important pharmacological activities
Retrieved from the P. lobata transcriptome, the full-length cDNAs of PlOMT3 and PlOMT4 were amplified by standard RT-PCRs, and their sequences were confirmed by sequencing and deposited in GenBank with the accession numbers of KP057886 and KP057887, respectively
PlOMT3 and PlOMT4 clustered with the flavonoid 3 -OMTs, suggesting that they are the candidates for the isoflavone 3 -O-methylation in P. lobata
Summary
Pueraria lobata (P. lobata) is a leguminous plant with important pharmacological activities. The medical effects of P. lobata are mostly attributed to the presence of a bioactive ingredient puerarin in its roots As a C-glucosylated isoflavone, puerarin exhibits diverse medicinal properties, especially shows the pharmacological activities on cardiovascular and cerebrovascular diseases (Wong et al, 2011; Zhou et al, 2014). Compared to the puerarin itself, its derivative 3 -methoxy-puerarin owns higher liposolubility and antioxidant activity, and better intracellular compartmentation (Heim et al, 2002; Yang et al, 2004; Zhang et al, 2008; Jin et al, 2012). Recent studies showed an obvious protective effect of 3 -methoxy-puerarin on cerebral ischemic-reperfusion injury with some advantages over puerarin (Chen, 2007; Zhang et al, 2008; Han et al, 2009). Considering the better performance of the 3 -methoxy-puerarin, it deserves to identify
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