Biosynthesis & Bioengineering
Natural product biosynthetic pathways have evolved impressive enzymatic machineries for the assembly of complex small molecules. These enzymes often catalyze unprecedented reactions that are highly exciting to investigate - out of pure scientific curiosity, but also for potential applications as biocatalysts. We explore whole pathways and individual enzymatic steps by combining heterolgous pathway expression, gene-knock-outs for functional studies, as well as in-depth in vitro characterization of individual enzymes. In addition, refactoring pathways is applied to study function and increase the diversity of its accessible products.
An interesting example is the biosynthetic pathway leading to ikarugamycin, a polycyclic tetramate-containing macrolactam (PoTeM). We have firmly established a highly unusual bacterial iterative polyketide synthase / non-ribosomal peptide synthetase (iPKS/NRPS) system IkaA combined with only two reductive enzymes IkaB and IkaC to be sufficient for the biosynthetic assembly of this impressively complex molecule.
The entire ikarugamycin biosynthetic machinery can be produced as recombinant enzymes and applied to its fully enzymatic total synthesis, a one pot overnight reaction! The efficiency of this procedure is in sharp contrast to the complexity of all total synthetic efforts towards PoTeMs developed to date and attests to the potential of such enzymatic approaches for complex molecule assembly. Additionally, further functionalization can be achived by emplying oxidative enzymes of related PoTeM pathways, for example for the conversion of ikarugamycin to its hydroxylated congener butremycin.
Further Reading:
J. Antosch, F. Schaefers, T. A. M. Gulder; Heterologous Reconstitution of Ikarugamycin Biosynthesis in E. coli; Angew. Chem. Int. Ed. 2014, 53, 3011-3014.
C. Greunke, J. Antosch, T. A. M. Gulder; Promiscuous Hydroxylases for the Functionalization of Polycyclic Tetramates Macrolactams - Conversion of Ikarugamycin to Butremycin; Chem. Commun. 2015, 51, 5334-5336.
C. Greunke, A. Glöckle, J. Antosch, T. A. M. Gulder; Biocatalytic Total Synthesis of Ikarugamycin ; Angew. Chem. Int. Ed. 2017, 56, 4351-4355.