Identification of key residues for activities of atypical glutathione S-transferase of Ceriporiopsis subvermispora, a selective degrader of lignin in woody biomass, by crystallography and functional mutagenesis

Enzymatic Degradation of Deoxynivalenol with the Engineered Detoxification Enzyme Fhb7

In the era of global climate change, the increasingly severe Fusarium head blight (FHB) and deoxynivalenol (DON) contamination have caused economic losses and brought food and feed safety concerns. Recently, an FHB resistance gene Fhb7 coding a glutathione-S transferase (GST) to degrade DON by opening the critical toxic epoxide moiety was identified and opened a new window for wheat breeding and DON detoxification. However, the poor stability of Fhb7 and the elusiveness of the catalytic mechanism hinder its practical application. Herein, we report the first structure of Fhb7 at 2.41 Å and reveal a unique catalytic mechanism of epoxide opening transformation in GST family proteins. Furthermore, variants V29P and M10 showed that 5.5-fold and 266.7-fold longer half-life time than wild-type, respectively, were identified. These variants offer broad substrate scope, and the engineered biosafe Bacillus subtilis overexpressing the variants shows excellent DON degradation performance, exhibiting potential at bacterium engineering to achieve DON detoxification in the feed and biomedicine industry. This work provides a profound mechanistic insight into the enzymatic activities of Fhb7 and paves the way for further utilizing Fhb7-related enzymes in crop breeding and DON detoxification by synthetic biology.

Catalytic and molecular properties of alkaliphilic and thermotolerant β-etherase from Altererythrobacter sp. B11

Phenylpropanone monomers, including guaiacyl hydroxypropanone, are important precursors for the synthesis of various chemicals. The monomers are obtained in a three-step cascade reaction catalyzed by a group of enzymes in the β-etherase system that cleaves the β-O-4 bond, the major bond in lignin. In this study, one of the β-etherase of the glutathione-S-transferase superfamily, AbLigF2, was discovered in genus Altererythrobacter, and the recombinant etherase was characterized. The enzyme showed maximal activity at 45 °C, maintained 30% of its activity after 2 h at 50 °C, and was the most thermostable among the previously reported enzymes. Moreover, N13, S14, and S115, located near the thiol group of glutathione, had a significant effect on the maximum reaction rate of enzyme activity. This study suggests that AbLigF2 has the potential to serve as a thermostable enzyme for lignin utilization and provides insights into its catalytic mechanism.

Assessments on the molecular toxic mechanisms of fipronil and neonicotinoids with glutathione transferase Phi8

As the most widely used pesticides, fipronils and neonicotinoids exhibit harmful effects to many species including crops mainly via the oxidative damages. However, the potential toxic mechanisms of these pesticides to plants remain unclear. In this work, glutathione S-transferase Phi8 was employed as the biomarker to assess the adverse oxidative effects of these two kinds of pesticides. The structural changes and binding characteristics of AtGSTF8 with the pesticides were investigated by multispectral techniques and the latest generation neonicotinoid dinotefuran exhibited the most evident effects on the structure of AtGSTF8. Then dinotefuran displayed weak binding ability to AtGSTF8 comparing with fipronil and clothianidin based on the bio-layer interferometry technique. Besides, the glutathione S-transferase activities of AtGSTF8 were decreased upon binding with these two kinds of pesticides but dinotefuran displayed minor effect on the enzyme activity. At last, dinotefuran and clothianidin were presumed to locate on the molecular surface of AtGSTF8, while fipronil was predicted to insert into the cavity of AtGSTF8 which was adjacent to the active G-site based on the molecular docking results. The molecular investigations on the toxic mechanisms would help to evaluate the harmful effects of these two kinds of prevalent pesticides to plants.