Understanding the glycopeptide antibiotic crosslinking cascade – in vitro approaches revealing the details of a complex biosynthesis pathway

The glycopeptide antibiotics (GPAs) are a fascinating example of complex natural product biosynthesis, with the non-ribosomal synthesis of the peptide core coupled to a cytochrome P450-mediated cyclisation cascade that crosslinks aromatic side chains within this peptide. Given the challenges associated with the synthesis of GPAs stems from their highly crosslinked structure, there is great interest in understanding how biosynthesis accomplishes this challenging set of transformations. In this regard, the use of in vitro experiments has delivered important insights into this process, including the identification of the unique role of the X-domain as a platform for P450 recruitment. In this mini-review, we present an analysis of the results of in vitro studies into the GPA cyclisation cascade, which has demonstrated both the tolerances and limitations of this process for modified substrates, and in turn developed rules for the future reengineering of this important antibiotic class.