Investigating Cytochrome P450 specificity during glycopeptide antibiotic biosynthesis through a homologue hybridization approach.

Cytochrome P450 enzymes perform an impressive range of oxidation reactions against diverse substrate scaffolds whilst generally maintaining a conserved tertiary structure and active site chemistry. Within secondary metabolism, P450 enzymes play widespread and important roles in performing crucial modifications of precursor molecules, with one example of the importance of such reactions being found in the biosynthesis of the glycopeptide antibiotics (GPAs). In GPA biosynthesis P450s, known as Oxy enzymes, are key players in the cyclization of the linear GPA peptide precursor, which is a process that is both essential for their antibiotic activity and is the source of the synthetic challenge of these important antibiotics. In this work, we developed chimeric P450 enzymes from GPA biosynthesis based on two homologues from different GPA biosynthesis pathways - vancomycin and teicoplanin - as an approach to explore the divergent catalytic behavior of the two parental homologues. We could generate, crystalize and explore the activity of new hybrid P450 enzymes from GPA biosynthesis and show that the unusual in vitro behavior of the vancomycin OxyB homologue does not stem from the major regions of the P450 active site, and that additional regions in and around the P450 active site must contribute to the unusual properties of this P450 enzyme. Our results further show that it is possible to successfully transplant entire regions of secondary structure between such P450s and retain P450 expression and activity, which opens the door to use such targeted approaches to generate and explore novel biosynthetic P450 enzymes.