Oxidative bicyclic ring system formation involving indole diterpene biosynthesis: Remarkable substrate tolerance of a prenyltransferase and flavoprotein oxidase

Oxidative modifications are key biosynthetic processes responsible for expanding the structural diversity of indole diterpenes (IDTs). In this study, we focused on the function of prenyltransferases and flavoprotein oxidases for the synthesis of nodulisporic acid-type and shearinine-type bicyclic rings found on the indole moiety. An in vitro enzymatic reaction of a prenyltransferase JanD, which mediates diprenylation at the C5- and C6-positions, revealed that JanD recognizes a C13 hydroxy group on the diterpene moiety. Subsequent enzymatic reactions with flavoprotein oxidases, JanO, and NodO, indicated that JanO can accommodate penta/hexacyclic IDTs, while NodO exhibits strict substrate specificity toward pentacyclic IDTs. The broad substrate tolerance of JanD and JanO provides opportunities for the synthesis of unnatural IDTs based on artificial reconstitution in a heterologous host.(c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

Oxidative modifications are essential for the biosynthesis of indole diterpenes (IDTs), and this study focused on the role of prenyltransferases and flavoprotein oxidases in the synthesis of nodulisporic acid-type and shearinine-type bicyclic rings on the indole moiety. The enzymatic reaction of prenyltransferase JanD showed that it recognizes a C13 hydroxy group on the diterpene moiety. Flavoprotein oxidases JanO and NodO exhibited different substrate specificities for penta/hexacyclic IDTs and pentacyclic IDTs, respectively.