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    Involvement of Sulfur in the Biosynthesis of Essential Metabolites in Pathogenic Fungi of Animals, particularly Aspergillus spp.: Molecular and Therapeutic Implications

    Traynor, Aimee M and Sheridan, Kevin J and Jones, Gary W and Calera, José A and Doyle, Sean (2019) Involvement of Sulfur in the Biosynthesis of Essential Metabolites in Pathogenic Fungi of Animals, particularly Aspergillus spp.: Molecular and Therapeutic Implications. Frontiers in Microbiology, 10 (2859). ISSN 1664-302X

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    Fungal sulfur uptake is required for incorporation into the sidechains of the amino acids cysteine and methionine, and is also essential for the biosynthesis of the antioxidant glutathione (GSH), S-adenosylmethionine (SAM), the key source of methyl groups in cellular transmethylation reactions, and S-adenosylhomocysteine (SAH). Biosynthesis of redox-active gliotoxin in the opportunistic fungal pathogen Aspergillus fumigatus has been elucidated over the past 10 years. Some fungi which produce gliotoxin-like molecular species have undergone unexpected molecular rewiring to accommodate this high-risk biosynthetic process. Specific disruption of gliotoxin biosynthesis, via deletion of gliK, which encodes a γ-glutamyl cyclotransferase, leads to elevated intracellular antioxidant, ergothioneine (EGT), levels, and confirms crosstalk between the biosynthesis of both sulfur-containing moieties. Gliotoxin is ultimately formed by gliotoxin oxidoreductase GliT-mediated oxidation of dithiol gliotoxin (DTG). In fact, DTG is a substrate for both GliT and a bis-thiomethyltransferase, GtmA. GtmA converts DTG to bisdethiobis(methylthio)gliotoxin (BmGT), using 2 mol SAM and resultant SAH must be re-converted to SAM via the action of the Methyl/Met cycle. In the absence of GliT, DTG fluxes via GtmA to BmGT, which results in both SAM depletion and SAH overproduction. Thus, the negative regulation of gliotoxin biosynthesis via GtmA must be counterbalanced by GliT activity to avoid Methyl/Met cycle dysregulation, SAM depletion and trans consequences on global cellular biochemistry in A. fumigatus. DTG also possesses potent Zn2+ chelation properties which positions this sulfur-containing metabolite as a putative component of the Zn2+ homeostasis system within fungi. EGT plays an essential role in high-level redox homeostasis and its presence requires significant consideration in future oxidative stress studies in pathogenic filamentous fungi. In certain filamentous fungi, sulfur is additionally indirectly required for the formation of EGT and the disulfide-bridge containing non-ribosomal peptide, gliotoxin, and related epipolythiodioxopiperazines. Ultimately, interference with emerging sulfur metabolite functionality may represent a new strategy for antifungal drug development.

    Item Type: Article
    Keywords: Aspergillus; sulfur; ergothioneine; gliotoxin; zinc;
    Academic Unit: Faculty of Science and Engineering > Biology
    Item ID: 13859
    Identification Number:
    Depositing User: Dr. Sean Doyle
    Date Deposited: 22 Jan 2021 11:34
    Journal or Publication Title: Frontiers in Microbiology
    Publisher: Frontiers Media
    Refereed: Yes
    Use Licence: This item is available under a Creative Commons Attribution Non Commercial Share Alike Licence (CC BY-NC-SA). Details of this licence are available here

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