21: Directed evolution of artificial metalloenzymes for ruthenium biocatalysis of polyketide like compounds

Abstract: Biocatalysis and directed evolution have provided the ability to harness enzymes catalytic properties in a tailor-made fashion. In the relatively recent development of Artificial Metalloenzymes (ArM), they have become an advanced tool utilizing the catalytic features of enzymes and the reaction scope of transition metals to provide creative strategies for synthetic development. ArM’s are made up of a scaffold protein and a tethered metal catalyst. The metal catalyst is embedded into the active site or cavity of the protein scaffold and as the catalyst promotes the reaction the protein scaffolds spatial strain promotes intramolecular cyclization that would otherwise not occur in a normal synthetic process. Ruthenium (Ru) based catalyst, most notably the Grubbs catalyst is a biorthogonal catalyst that is reliably compatible with enzymatic conditions. Polyketides are bioactive natural products most well-known for antibiotic(Ex: erythromycin) and antifungal(Ex: amphotericin B) properties. As more natural products are found the novelty of these polyketides decreases and ultimately reduces novel bioactive compounds. Developing polyketide-like compounds could expand the known chemical space of bioactive compounds. This is accomplished by the forced intramolecular cyclization with a library of protein scaffolds, ruthenium tether ligands and substrates to develop a semi-random array of polyketide like compounds that can be then tested for bioactivities. The yield could then be further improved by using directed evolution with protein scaffolds of interest.