Rauvolfia serpentina N-methyltransferases involved in ajmaline and Nβ-methylajmaline biosynthesis belong to a gene family derived from γ-tocopherol C-methyltransferase
Rauvolfia serpentina N-methyltransferases involved in ajmaline and Nβ-methylajmaline biosynthesis belong to a gene family derived from γ-tocopherol C-methyltransferase
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DOI：
10.1111/tpj.13186
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发表时间：
2016-08-01
期刊：
影响因子：
7.2
通讯作者：
De Luca, Vincenzo
中科院分区：
文献类型：
--
作者：
Cazares-Flores, Paulo;Levac, Dylan;De Luca, Vincenzo
罗布麻碱的生物合成一直是夹竹桃科植物中被研究最多的单萜类吲哚生物碱途径之一。在过去的30年里，已经产生了关于该途径中涉及的大多数步骤的详细的分子和生化信息。在这里，我们报道了两个蛇纹菌cDNAs的鉴定、分子克隆和功能表达，它们是最近发现的一个γ-生育酚样N-甲基转移酶(Gamma-TLMT)家族的一部分，并参与了Ajmarine的吲哚和侧链N-甲基化。重组蛋白对具有阿玛兰型骨架和严格区域特异性N-甲基化的分子表现出显著的底物特异性。此外，蛇床子根中N-甲基转移酶基因转录本和酶活性丰富，这与艾季马林生物碱的积累有关。本研究阐明了艾吉马林生物合成途径的最后一步，并描述了负责形成N-β-甲基马林的酶，N-β-甲基马林是在蛇纹夜蛾中发现的一种不寻常的带电MIA。
Ajmaline biosynthesis in Rauvolfia serpentina has been one of the most studied monoterpenoid indole alkaloid (MIA) pathways within the plant family Apocynaceae. Detailed molecular and biochemical information on most of the steps involved in the pathway has been generated over the last 30 years. Here we report the identification, molecular cloning and functional expression in Escherichia coli of two R. serpentina cDNAs that are part of a recently discovered gamma-tocopherol-like N-methyltransferase (gamma-TLMT) family and are involved in indole and side-chain N-methylation of ajmaline. Recombinant proteins showed remarkable substrate specificity for molecules with an ajmalan-type backbone and strict regiospecific N-methylation. Furthermore, N-methyltransferase gene transcripts and enzyme activity were enriched in R. serpentina roots which correlated with accumulation of ajmaline alkaloid. This study elucidates the final step in the ajmaline biosynthetic pathway and describes the enzyme responsible for the formation of N-beta-methylajmaline, an unusual charged MIA found in R. serpentina.