Studies on terpenoids produced by actinomycetes-Screening for new bioactive compounds

本项目的目的是从放线菌中分离新的萜类化合物，并研究其化学和生物学性质。为了实现这一目的，我们首先尝试通过使用HMG-CoA还原酶基因作为PCR探针来分离具有甲羟戊酸途径的放线菌，甲羟戊酸途径的关键酶，然后从微生物中分离萜类化合物。与我们的预期相反，分离的阳性菌株的数量非常少，但我们成功地纯化了几个新的萜类化合物。其中，一个化合物被证明是一个新的二萜衍生物与isopimaradiene骨架，从来没有被分离的放线菌代谢产物。虽然由于专利申请的原因，该新化合物的详细性质不能公开，但它对EGF蛋白酪氨酸激酶具有很强的抑制活性，其详细的生物活性正在研究中。为了揭示甲羟戊酸途径与萜类化合物生物合成的关系，本项目对产萜类化合物放线菌的相关基因进行了研究。结果发现，在甲羟戊酸途径基因簇周围存在与萜类生物合成相关的基因。这一发现表明甲羟戊酸途径与萜类化合物的产生密切相关。这些基因的表达被观察到在生产生物体的生长的后期阶段，当次级代谢产物的生产started.Inhibition的甲羟戊酸途径在一个链霉菌菌株与甲羟戊酸途径引起积累的一个新的化合物，mevashuntin。这些信息对放线菌产萜类化合物的研究具有重要意义。

The purpose of this project is to isolate new terpenoids from Actinomycetes and to investigate their chemical and biological properties. In order to achieve this purpose, we first attempted to isolate actinomycetes possessing the mevalonate pathway by using the HMG-CoA reductase gene as a probe for PCR, the key enzyme of the mevalonate pathway, and then to isolate terpenoids from the microorganisms. Contrary to our expectation, the number of positive strains isolated was very small, but we succeeded in purification of several new terpenoids. Among them, one compound proved to be a new diterpene derivative with the isopimaradiene skeleton that has never been isolated as actinomycetes metabolites. Although detail properties of this new compound can not be disclosed due to patent application, it showed strong inhibitory activity to EGF protein tyrosine kinase and its detailed biological activities are now under investigation. Another new terpenoid was also isolated from another strain of Streptomyces.In order to disclose the relationship between the mevalonate pathway and terpenoid biosynthesis, the relevant genes of actinomycetes producing terpenoids were investigated in this project. As a result, it turned out that genes related to terpenoid biosynthesis existed around the mevalonate pathway gene cluster. This finding shows that the mevalonate pathway is strictly linked to production of terpenoids. Expression of these gene was observed at the later stage of the growth of the producing organisms when the production of secondary metabolites started.Inhibition of the mevalonate pathway in one Streptomyces strain with the mevalonate pathway caused accumulation of a new compound, mevashuntin. The obtained information is expected to be important for studies related to production of terpenoids by actinomycetes.