Assessing the beneficial aspects of endophytic actinobacteria: expanding the Brazilian microorganisms genome codified natural products

Abstract

Terpenes and terpenoids represent the widest class of natural products found in nature. Despite their structural diversity, all terpenoids are biosynthesized from two chemically related molecules, namely ”1- and ”2-isopentenyl diphosphate. The isopentenyl diphosphates are joined in elongation reactions to form the linear precursors of all terpenoids. The action of terpene synthases then converts these linear precursors into a large number of cyclic products. Near to 75000 terpenes/terpenoids are known so far and only 235 has its biosynthetic origin associated with Streptomyces according to the Dictionary of Natural Products. Historically the most part of the studies on terpenes was performed on plants and fungi. Bacteria were recognized as a source for such metabolites in the most recent time. In the current grant call, we are proposing to promote mechanistic studies and the expansion of the terpenome from actinobacteria isolated in Brazilian territory. Until the moment we were able to clone and express several cyclases annotated from the Streptomyces genome by using genome-mining approaches. The most part of the TS deriving from actinobacteria can be expressed in E. coli by using synthetic genes. In vitro studies of these proteins in the presence of precursors as FPP, GPP, GGPP are capable to reproduce the cyclization reactions for cyclic terpenes. The first experiments of precursors incubation of the terpene synthases show that the enzymes are active and capable to convert FPP into terpenes with no precedent structure reported in the literature. Therefore fundamental knowledge on the chemical space of sesquiterpene synthases, structural limits that are placed on the activity of enzyme active sites and fundamental mechanisms by which enzymes control selectivity and specificity are questions to be addressed at this moment. This work will provide very promising results to the understanding of mechanisms involved in terpene biosynthesis and how to expand the knowledge of such an important and versatile group of metabolites. (AU)