Discovery of UbiA-Type Cyathane Synthases in Bacteria

UbiA-type terpene synthases, traditionally annotated as prenyltransferases, have been shown to catalyze terpene cyclization in recent years, expanding their catalytic repertoire beyond primary metabolism. Here, we report on the genome-guided discovery and functional characterization of bacterial UbiA diterpene synthases (diTSs). Using a geranylgeranyl diphosphate (GGPP)-overproducing Escherichia coli system, we screened 32 candidate enzymes and identified five that generate structurally diverse diterpenes, two of which represent bacterial examples of cyathane synthases. Site-directed mutagenesis uncovered active-site residues that influence product formation, directing cyclization toward mono- or tricyclic products. This study expands the known catalytic repertoire of UbiA enzymes and highlights their untapped potential in bacterial terpenoid biosynthesis. Our findings suggest that bacteria may produce diverse and bioactive diterpenoids using UbiA TSs for the first committed biosynthetic step, warranting further exploration of UbiA TSs for natural product discovery.