Thiopeptides are a growing class of ribosomally synthesized and post-translationally modified peptide, RiPP, natural products. Many biosynthetic enzymes for RiPPs, especially thiopeptides, are promiscuous and can accept a wide range of peptide substrates with different amino acid sequences; thus, these enzymes have been used as tools to generate new natural product derivatives.
In work published in ACS Chemical Biology, researchers in the Brustad Group, in collaboration with members of the Bowers Group with UNC's Eshelman School of Pharmacy, explore an alternative route to molecular complexity by engineering thiopeptide tailoring enzymes to do new or non-native chemistry.
The group members explore cytochrome P450 enzymes as biocatalysts for cyclopropanation of dehydroalanines, chemical motifs found widely in thiopeptides and other RiPP-based natural products. They found that P450TbtJ1 and P450TbtJ2 selectively cyclopropanate dehydroalanines in a number of complex thiopeptide-based substrates and convert them into 1-amino-2-cyclopropane carboxylic acids, ACCAs, which are important pharmacophores.
This chemistry takes advantage of the innate affinity of these biosynthetic enzymes for their substrates and enables incorporation of new pharmacophores into thiopeptide architectures. The work also presents a strategy for diversification of natural products through rationally repurposing biosynthetic enzymes as non-natural biocatalysts.