The fungal glutathione S-transferase system. Evidence of new classes in the wood-degrading basidiomycete Phanerochaete chrysosporium

Abstract

The recent release of several basidiomycete genome sequences allows an improvement of the classification of fungal glutathione S-transferases (GSTs). GSTs are well-known detoxification enzymes which can catalyze the conjugation of glutathione to non-polar compounds that contain an electrophilic carbon, nitrogen, or sulfur atom. Following this mechanism, they are able to metabolize drugs, pesticides, and many other xenobiotics and peroxides. A genomic and phylogenetic analysis of GST classes in various sequenced fungi--zygomycetes, ascomycetes, and basidiomycetes--revealed some particularities in GST distribution, in comparison with previous analyses with ascomycetes only. By focusing essentially on the wood-degrading basidiomycete Phanerochaete chrysosporium, this analysis highlighted a new fungal GST class named GTE, which is related to bacterial etherases, and two new subclasses of the omega class GSTs. Moreover, our phylogenetic analysis suggests a relationship between the saprophytic behavior of some fungi and the number and distribution of some GST isoforms within specific classes.

Transcriptomic Responses of Phanerochaete chrysosporium to Oak Acetonic Extracts: Focus on a New Glutathione Transferase

“…Based on sequence homology, it appears that the Phanerochaete isoform belongs to MGST3, but it has not been functionally characterized yet. GSTFuA3 belongs to a newly identified GST class (18,45). Four members of this class (GSTFuA1 to GSTFuA4) exhibit a ligandin property toward wood compounds, such as coniferaldehyde, syringaldehyde, vanillin, chloronitrobenzoic acid, hydroxyacetophenone, and catechins, suggesting a role in sequestration and transport of the toxic molecules inside the cell (14,45).…”

“…GSTFuA3, which is the only member of this family that is able to reduce peroxides, is induced in our study, while GSTFuA1 and GSTFuA2 are downregulated. GTT2.1 was first defined by its sequence homology to GTT2 from S. cerevisiae (18). ScGTT2 exhibits GST activity with CDNB and seems to be crucial in the response to peroxides (46)(47)(48).…”

“…To date, no other fungal homologue has been characterized. In P. chrysosporium, 2 GTT2-related (Joint Genome Institute [JGI] protein identifiers [ProtID] 6683 and 6766) and no GTT1 genes have been identified in the genome by sequence homology with the yeast isoforms (18). However, their roles are unknown.…”

Characterization of a Phanerochaete chrysosporium Glutathione Transferase Reveals a Novel Structural and Functional Class with Ligandin Properties

“…Etherase-like GSTs are fungal specific, although they show weak homology with LigE, a bacterial protein responsible for the cleavage of ␤-aryl ether linkages of lignin in Sphingobium sp. SYK-6 (8,17). The etherase-like class is expanded in wood decaying fungi, because, for instance, 11 etherase-like encoding genes are present in the genome of Postia placenta.…”

Initial Proteomic Identification of Secreted Proteins of White-Rot Fungus Porodaedalea pini Grown on Liquid Medium

“…12 and 20, were identified as alcohol dehydrogenase and glutathione S-transferase, respectively, being related to aromatic compound metabolism and defence agains oxidative stress [23,26]. White-rot fungi use and regulate unique metabolic protein for degrading a variety of aromatic compounds, such as alcohol dehydrogenase and glutathione S-transferase [10,23,27]. These proteins play an important role in cleavage of the β-aryl ether linkage of high molecular lignin [28] and support lignin degradation; although, the precise mechanisms of these enzymes remain unresolved [10,29].…”