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Bioactive dimeric (pre‐)anthraquinones are ubiquitous in nature and are found in bacteria, fungi, insects, and plants. Their biosynthesis via oxidative phenol coupling (OPC) is catalyzed by cytochrome P450 enzymes, peroxidases, or laccases. While the biocatalysis of OPC in molds (Ascomycota) is well‐known, the respective enzymes in mushroom‐forming fungi (Basidiomycota) are unknown. Here, we report on the biosynthesis of the atropisomers phlegmacin A1 and B1 of the mushroom Cortinarius odorifer. The biosynthesis of these unsymmetrically 7,10'‐homo‐coupled dihydroanthracenones was heterologously reconstituted in the mold Aspergillus niger. Methylation of the parental monomer atrochrysone to its 6‐O‐methyl ether torosachrysone by the O‐methyltransferase CoOMT1 precedes the regioselective homocoupling to phlegmacin, catalyzed by the enzyme CoUPO1 annotated as an "unspecific peroxygenase" (UPO). Our results reveal an unprecedented UPO reaction, thereby expanding the biocatalytic portfolio of oxidative phenol coupling beyond the commonly reported enzymes. The results show that Basidiomycota use peroxygenases to selectively couple aryls independently of and convergently to any other group of organisms, emphasizing the central role of OPC in natural processes. [ABSTRACT FROM AUTHOR]

Bioaktive dimere (Prä‐)Anthrachinone sind in der Natur allgegenwärtig und kommen in Bakterien, Pilzen, Insekten und Pflanzen vor. Ihre Biosynthese durch oxidative Phenolkupplung (OPC) wird durch Cytochrom P450‐Enzyme, Peroxidasen oder Laccasen katalysiert. Während die Biokatalyse der OPC in Schimmelpilzen (Ascomycota) bekannt ist, sind die entsprechenden Enzyme in Ständerpilzen (Basidiomycota) noch unbekannt. Hier stellen wir die Biosynthese der Atropisomere Phlegmacin A1 und B1 aus dem Pilz Cortinarius odorifer vor. Die Biosynthese des unsymmetrisch 7,10'‐homogekuppelten Dihydroanthracenons wurde im Schimmelpilz Aspergillus niger heterolog rekonstruiert. Die Methylierung des Monomers Atrochryson zum 6‐O‐Methylether Torosachryson durch die O‐Methyltransferase CoOMT1 geht der regioselektiven Homokupplung zu Phlegmacin voraus, welche durch das Enzym CoUPO1 katalysiert wird, die zu den als Unspezifische Peroxygenase (UPO) bezeichneten Enzymen Sequenzhomologie zeigt. Unsere Ergebnisse belegen eine noch unbeschriebene UPO‐Reaktion und erweitern damit das biokatalytische Portfolio der OPC über die zuvor bekannten Enzyme hinaus. Die Ergebnisse zeigen, dass Basidiomycota Peroxygenasen nutzen, um Aryle selektiv zu kuppeln, und zwar unabhängig von und konvergent zu jeder anderen Organismengruppe, was die zentrale Rolle der OPC in der Naturstoffchemie unterstreicht. [ABSTRACT FROM AUTHOR]

(Pre-)anthraquinones are widely distributed natural compounds and occur in plants, fungi, microorganisms, and animals, with atrochrysone (1) as the key biosynthetic precursor. Chemical analyses established mushrooms of the genus Cortinarius-the webcaps-as producers of atrochrysone-derived octaketide pigments. However, more recent genomic data did not provide any evidence for known atrochrysone carboxylic acid (4) synthases nor any other polyketide synthase (PKS) producing oligocyclic metabolites. Here, we describe an unprecedented class of non-reducing (NR-)PKS. In vitro assays with recombinant enzyme in combination with in vivo product formation in the heterologous host Aspergillus niger established CoPKS1 and CoPKS4 of C. odorifer as members of a new class of atrochrysone carboxylic acid synthases. CoPKS4 catalyzed both hepta- and octaketide synthesis and yielded 6-hydroxymusizin (6), along with 4. These first mushroom PKSs for oligocyclic products illustrate how the biosynthesis of bioactive natural metabolites evolved independently in various groups of life., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)