Substrate and catalytic promiscuity of secondary metabolite enzymes: O-prenylation of hydroxyxanthones with different prenyl donors by a bisindolyl benzoquinone C- and N-prenyltransferase

Abstract

Prenylated xanthones are secondary metabolites with a broad spectrum of biological activities including antimicrobial and antitumor activities. One xanthone O-prenyltransferase XptB has been identified in Aspergillus nidulans. Recently, we characterised a bisindolyl benzoquinone C- and N-prenyltransferase AstPT from Aspergillus terreus with unusually high substrate specificity towards both the prenyl donor dimethylallyl diphosphate and acceptor bisindolyl benzoquinone. In this study, we demonstrate the acceptance of a number of hydroxyxanthones by AstPT in the presence of not only dimethylallyl but also geranyl and farnesyl diphosphate. Structural elucidation by HR-MS and NMR analyses proved the O-prenylation of all thirteen isolated enzyme products with different prenyl moieties. These results demonstrated the remarkable substrate and catalytic promiscuity of AstPT, which was recognised as a specific enzyme prior to this study.