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

经典的萜类化合物生物合成是基于C10-GPP、C15-FPP或C20-GGPP作为底物，但必须考虑范式变化。FPP甲基转移酶与非经典萜烯合成酶的c -甲基化和环化耦合代表了一种前所未有的反应机制，最近在沙雷氏菌4Rx13中被证明是独特的索多利芬生物合成。它说明了由于利用C16底物而扩大萜烯多样性的另一种途径。随后的sodorifen合成酶对非规范的单环前sodorifen焦磷酸盐的底物特异性意味着这两种酶的共同进化。在产生新型双同萜类氯酚的绿假单胞菌O6中也发现了这种共同进化的初步证据。到目前为止，丙烯基焦磷酸酯的c -甲基化和环化仅在细菌中发现，仔细研究了各自生物合成途径的起源。我们推测，在变形菌中，而不是在放线菌中（如链霉菌），FPP的c -甲基化和环化被建立在新的萜类化合物的生物合成中。在这里，我们将验证C17化合物氯酚的生物合成是否依赖于之前的两个甲基转移酶反应，然后是萜烯合成酶反应。此外，我们将验证FPP甲基转移酶在进化过程中是否（完全/主要）表现在变形菌中。

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.