Regioselective Oxidative Phenol Coupling by a Mushroom Unspecific Peroxygenase.

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.

The Ketosynthase Domain Controls Chain Length in Mushroom Oligocyclic Polyketide Synthases.

The nonreducing iterative type I polyketide synthases (NR-PKSs) CoPKS1 and CoPKS4 of the webcap mushroom Cortinarius odorifer share 88 % identical amino acids. CoPKS1 almost exclusively produces a tricyclic octaketide product, atrochrysone carboxylic acid, whereas CoPKS4 shows simultaneous hepta- and octaketide synthase activity and also produces the bicyclic heptaketide 6-hydroxymusizin. To identify the region(s) controlling chain length, four chimeric enzyme variants were constructed and assayed for activity in Aspergillus niger as heterologous expression platform.

Unprecedented Mushroom Polyketide Synthases Produce the Universal Anthraquinone Precursor.

(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.