Publications

• Heterologous biosynthesis of elsinochrome A sheds light on the formation of the photosensitive perylenequinone system.

  Hu J., Sarrami F., Li H., Zhang G., Stubbs K.A., Lacey E., Stewart S.G., Karton A., Piggott A.M., Chooi Y.H.

  Perylenequinones are a class of aromatic polyketides characterised by a highly conjugated pentacyclic core, which confers them with potent light-induced bioactivities and unique photophysical properties. Despite the biosynthetic gene clusters for the perylenequinones elsinochrome A (<b>1</b>), cer ... >> More

  Perylenequinones are a class of aromatic polyketides characterised by a highly conjugated pentacyclic core, which confers them with potent light-induced bioactivities and unique photophysical properties. Despite the biosynthetic gene clusters for the perylenequinones elsinochrome A (<b>1</b>), cercosporin (<b>4</b>) and hypocrellin A (<b>6</b>) being recently identified, key biosynthetic aspects remain elusive. Here, we first expressed the intact <i>elc</i> gene cluster encoding <b>1</b> from the wheat pathogen <i>Parastagonospora nodorum</i> heterologously in <i>Aspergillus nidulans</i> on a yeast-fungal artificial chromosome (YFAC). This led to the identification of a novel flavin-dependent monooxygenase, ElcH, responsible for oxidative enolate coupling of a perylenequinone intermediate to the hexacyclic dihydrobenzo(<i>ghi</i>)perylenequinone in <b>1</b>. In the absence of ElcH, the perylenequione intermediate formed a hexacyclic cyclohepta(<i>ghi</i>)perylenequinone system <i>via</i> an intramolecular aldol reaction resulting in <b>6</b> and a novel hypocrellin <b>12</b> with opposite helicity to <b>1</b>. Theoretical calculations supported that <b>6</b> and <b>12</b> resulted from atropisomerisation upon formation of the 7-membered ring. Using a bottom-up pathway reconstruction approach on a tripartite YFAC system developed in this study, we uncovered that both a berberine bridge enzyme-like oxidase ElcE and a laccase-like multicopper oxidase ElcG are involved in the double coupling of two naphthol intermediates to form the perylenequinone core. Gene swapping with the homologs from the biosynthetic pathway of <b>4</b> showed that cognate pairing of the two classes of oxidases is required for the formation of the perylenequinone core, suggesting the involvement of protein-protein interactions. << Less

  Chem. Sci. 10:1457-1465(2019) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Molecular characterization of the cercosporin biosynthetic pathway in the fungal plant pathogen Cercospora nicotianae.

  Newman A.G., Townsend C.A.

  Perylenequinones are a class of photoactivated polyketide mycotoxins produced by fungal plant pathogens that notably produce reactive oxygen species with visible light. The best-studied perylenequinone is cercosporin-a product of the Cercospora species. While the cercosporin biosynthetic gene clus ... >> More

  Perylenequinones are a class of photoactivated polyketide mycotoxins produced by fungal plant pathogens that notably produce reactive oxygen species with visible light. The best-studied perylenequinone is cercosporin-a product of the Cercospora species. While the cercosporin biosynthetic gene cluster has been described in the tobacco pathogen Cercospora nicotianae, little is known of the metabolite's biosynthesis. Furthermore, in vitro investigations of the polyketide synthase central to cercosporin biosynthesis identified the naphthopyrone nor-toralactone as its direct product-an observation in conflict with published biosynthetic proposals. Here, we present an alternative biosynthetic pathway to cercosporin based on metabolites characterized from a series of biosynthetic gene knockouts. We show that nor-toralactone is the key polyketide intermediate and the substrate for the unusual didomain protein CTB3. We demonstrate the unique oxidative cleavage activity of the CTB3 monooxygenase domain in vitro. These data advance our understanding of perylenequinone biosynthesis and expand the biochemical repertoire of flavin-dependent monooxygenases. << Less

  J. Am. Chem. Soc. 138:4219-4228(2016) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.