Biocatalysts for Peptide Geranylation With Linear and Cyclic Prenyl Groups

Prenylation improves the bioactivity and therapeutic properties of peptides from natural product and synthetic origin. Prenyltransferases (PTs) catalyze peptide prenylation under mild conditions with often remarkable chemo- and regioselectivity. Representatives from structurally distinct prenyltransferase families involved in ribosomal peptide biosynthesis revealed a large potential for chemoenzymatic peptide functionalization with linear prenyl donors. In contrast, the prenyltransferase-terpene cyclase fusion enzyme NctPC installs a polycyclic isoprenoid moiety during biosynthesis of the ribosomal peptide natural product steromaze. However, the two characterized steromaze-like PTs require at least the presence of a macrocyclic (methyl) lanthionine ring as a prerequisite for prenylation. Here, we report the characterization of standalone NctPC homologs, the steromaze-like prenyltransferase NdnP and the terpene cyclase NdnC, further expanding the chemical space of ribosomal peptides with cyclic isoprenoid moieties. NdnP is highly promiscuous for the geranylation of peptides containing C-terminal tryptophan from ribosomal and synthetic origins without being leader- or modification-dependent. The terpene cyclase NdnC utilizes the geranylated tryptophan to yield a tetracyclic amino acid at the peptide C-terminus. The promiscuity of both enzymes for ribosomal and synthetic peptides makes them promising biocatalysts for lipopeptide drug development, creating so far enzymatically inaccessible peptide terpenoid hybrids.