Discovery and Heterologous Expression of Functional 4-O-Dimethylallyl-<sc>l</sc>-tyrosine Synthases from Lichen-Forming Fungi

Fungal aromatic prenyltransferases are a family of biosynthetic enzymes that catalyze the prenylation of a range of aromatic substrates during the biosynthesis of bioactive indole alkaloids, diketopiperazines, and meroterpenoids. Their broad substrate scope and soluble nature make these enzymes particularly adept for applications in biocatalysis; for example, the enzymatic derivatization of aromatic drugs improves their bioactivity. Here, we investigated four putative aromatic prenyltransferases from lichen-forming fungi, an underexplored group of organisms that produce more than 1,000 unique metabolites. We successfully expressed two enzymes, annotated as dimethylallyltryptophan synthases, from two lichen species in the heterologous host A. oryzae. Based on their in vivo activity, we hypothesize that these enzymes are in fact 4-O-dimethylallyl-l-tyrosine synthases. Our extensive bioinformatic analysis further confirmed that these and related lichen aromatic prenyltransferases are likely not active on indoles but rather on aromatic polyketides and phenylpropanoids, major metabolites in lichens. Overall, our work provides new insights into fungal aromatic prenyltransferases at the family level and enables future efforts aimed at identifying new candidates for biocatalytic transformations of aromatic compounds.