Elucidation of novel FPP-methyltransferase-terpene synthase gene clusters in Proteobacteria

萜类化合物的经典生物合成是基于使用C10-GPP、C15-FPP或C20-GGPP作为底物，但必须考虑范式的改变。通过FPP甲基转移酶与非经典萜烯合酶的C-甲基化和环化的偶联代表了一种前所未有的反应机制，该反应机制最近被证明是Serratia sodorifen在Serratia muthica 4 Rx 13中的独特生物合成。它说明了一种替代途径，以扩大萜烯多样性，由于利用C16基板。底物特异性的非典型的，单环的前sodorifen焦磷酸钠的后续sodorifen合酶意味着这两种酶的共同进化。这种共同进化的初步额外证据也发现在绿针假单胞菌O 6，它产生新的双-高萜氯萝卜。到目前为止，异戊烯焦磷酸的C-甲基化和环化反应仅在细菌中发现，这些细菌正在仔细研究各自生物合成途径的起源。我们推测，在变形菌，而不是在放线菌（如链霉菌属）的C-甲基化和环化FPP的生物合成新的萜类化合物。在这里，我们将验证是否C17化合物chlororaphen的生物合成取决于两个前面的甲基转移酶反应，然后由萜烯合酶反应。此外，我们将测试的假设是否FPP甲基转移酶（排他性/显性）表现在变形菌在进化过程中。

The classical biosynthesis of terpenoids is based on the usage of C10-GPP, C15-FPP or C20-GGPP as substrates, but a paradigm change has to be considered. A coupling of C-methylation and cyclization by the FPP methyltransferase with a non-classical terpene synthase represents an unprecedented reaction mechanism which was recently shown for the unique biosynthesis of sodorifen in Serratia plymuthica 4Rx13. It illustrates an alternative avenue to enlarge terpene diversity due to the utilization of a C16 substrate. Substrate specificity of the succeeding sodorifen synthase for the non-canonical, monocyclic pre-sodorifen pyrosphosphate implies the coevolution of both enzymes. Preliminary additional evidence of this coevolution is also found in Pseudomonas chlororaphis O6 which produces the novel bis-homoterpene chlororaphen. So far, C-methylations and cyclizations of prenyl pyrophosphates have been exclusively found in bacteria scrutinizing the origin of respective biosynthetic pathways. We hypothesize that in proteobacteria rather than in actinobacteria (e.g. Streptomyces species) C-methylation and cyclization of FPP was established for the biosynthesis of novel terpenoids. Here we will verify whether the biosynthesis the of C17 compound chlororaphen depends on two preceding methyltransferase reactions which are followed by a terpene synthase reaction. Moreover, we will test the hypothesis whether FPP methyltransferases were (exclusively/dominantly) manifested in proteobacteria during evolution.