Chemisch-biologische Untersuchung und Kontrolle der Phenazin-Biosynthese

The penazines are a large class of redox-active bacterial secondary metabolites that play an important role for cell survival by acting as antibiotics and virulence factors. Their biosynthesis may therefore be an interesting target for novel pharmaceuticals in the treatment of infectious disease. Phenazines derive from chorismic acid through a conserved pathway that involves enzymes encoded in the phz-operon. Despite progress in the general understanding of the process, important details are still unclear due the fact that phenazine biosynthesis proceeds through several unstable intermediates that are difficult to characterize. This proposal aims at filling the existing gaps by combining synthetic chemistry with biochemical and structural techniques. In particular, the applicants propose to 1. investigate differences between 2-amino-2-desoxyisochorismate (ADIC) synthase PhzE and the related anthranilate synthases, which convert ADIC further to anthranilate despite having a very similar active center; 2. gain detailed insight into PhzF, which catalyzes a [1,5]-prototropic shift that may follow a pericyclic reaction mechanism; 3. develop existing product analogues of PhzB into inhibitors of phenazine biosynthesis and 4. understand the biochemical relevance of PhzA/PhzB heterodimerization in pseudomonal phenazine producers. The collaboration of Dr. Blankenfeldt (MPI Dortmund, Germany) and Prof. Dr. Breinbauer (Graz University of Technology, Austria) ensures that these aims will be met within the three years funding period. The partners possess complementary expertises in organic synthesis, biochemistry and structural biology, and they have demonstrated a productive collaboration by contributing significantly to the field of phenazine biosynthesis in the recent years. Transnational funding will enable two PhD students to acquire broad expertise in methodologically heterogeneous areas, and the proposed research will make significant contributions not only by providing detailed descriptions of novel enzyme mechanisms but also tool compounds that can be employed as lead structures against infectious disease inflicted by phenazine -producing microorganisms.

Phenazine sind eine Klasse von redoxaktiven bakteriellen Sekundärmetaboliten, die eine wichtige Rolle für das Überleben dieser Bakterien darstellen, da sie als Antibiotika oder Virulenfaktoren dienen. Ihre Biosynthese könnte ein interessanter Angriffspunkt für neue Pharmazeutika darstellen. Phenazine werden aus Chorismatsäure in einem streng konservierten Weg synthetisiert, der von Enzymen kontrolliert wird die im phz- Operon codiert sind. In einer gemeinsamen Zusammenarbeit zwischen dem Strukturbiologen Prof. Wulf Blankenfeldt (Helmholtz Zentrum für Infektionsforschung, Braunschweig/Deutschland) und dem Organischen Chemiker Prof. Dr. Breinbauer (Technische Universität Graz/Österreich) wurden die mechanistischen Details der Phenazin-Biosynthese untersucht. Dabei haben sie auch Liganden des Proteins PhzB identifiziert, die ermutigende erste Ergebnisse für die Inhibierung der Biosynthese des Virulenzfaktors Pyocyanin in Pseudomonas aeruginosa ergaben.