Regioselective Oxidative Phenol Coupling by a Mushroom Unspecific Peroxygenase

Area of Science:

• Biochemistry and Molecular Biology
• Mycology
• Natural Product Biosynthesis

Background:

• Dimeric (pre-)anthraquinones are widespread natural products synthesized via oxidative phenol coupling (OPC).
• Enzymes like cytochrome P450s, peroxidases, and laccases catalyze OPC, but enzymes in mushroom-forming fungi (Basidiomycota) remain uncharacterized.
• The biosynthesis of OPC in molds (Ascomycota) is well-understood, highlighting a gap in knowledge for other fungal groups.

Purpose of the Study:

• To elucidate the biosynthesis of phlegmacin A1 and B1, atropisomers from the mushroom Cortinarius odorifer.
• To identify and characterize the enzymes responsible for OPC in Basidiomycota.
• To expand the known enzymatic repertoire for oxidative phenol coupling reactions.

Main Methods:

• Heterologous reconstitution of phlegmacin A1 and B1 biosynthesis in Aspergillus niger.
• Identification and functional characterization of the O-methyltransferase (CoOMT1) and unspecific peroxygenase (CoUPO1) involved.
• Analysis of regioselective homocoupling catalyzed by CoUPO1.

Main Results:

• The study identified CoOMT1 responsible for methylating atrochrysone to torosachrysone.
• CoUPO1, an unspecific peroxygenase, was found to catalyze the regioselective homocoupling of torosachrysone to produce phlegmacins.
• This represents an unprecedented reaction for unspecific peroxygenases, expanding the known biocatalytic scope of OPC.

Conclusions:

• Basidiomycota utilize unspecific peroxygenases for selective aryls coupling, independent of other organisms.
• This discovery reveals a novel enzymatic pathway for OPC, broadening the understanding of natural product biosynthesis.
• Oxidative phenol coupling plays a central and diverse role across different fungal lineages.