Structural and functional characterization of the glutathione peroxidase-like thioredoxin peroxidase from the fungus Trichoderma reesei

Glutathione peroxidases (GPx) are a family of enzymes with the ability to reduce organic and inorganic hydroperoxides to the corresponding alcohols using glutathione or thioredoxin as an electron donor. Here, we report the functional and structural characterization of a GPx identified in Trichoderma reesei (TrGPx). TrGPx was recombinantly expressed in a bacterial host and purified using affinity. Using a thioredoxin coupled assay, TrGPx exhibited activity of 28 U and 12.5 U in the presence of the substrates H2O2 and t-BOOH, respectively, and no activity was observed when glutathione was used. These results indicated that TrGPx is a thioredoxin peroxidase and hydrolyses H2O2 better than t-BOOH. TrGPx kinetic parameters using a pyrogallol assay resulted at K-mapp = 11.7 mM, V-maxapp = 10.9 IU/mu g TrGPx, k(cat) = 19 s(-1) and a catalytic efficiency of 1.6 mM(-1) s(-1) to H2O2 as substrate. Besides that, TrGPx demonstrated an optimum pH ranging from 9.0-12.0 and a half-life of 36 min at 80 degrees C. TrGPx 3D-structure was obtained in a reduced state and non-catalytic conformation. The overall fold is similar to the other phospholipid-hydroperoxide glutathione peroxidases. These data contribute to understand the antioxidantmechanism in fungi and provide information for using antioxidant enzymes in biotechnological applications. (C) 2020 Published by Elsevier B.V.

Automated summary

The study characterized the functional and structural features of a glutathione peroxidase (GPx) identified in Trichoderma reesei, demonstrating that TrGPx is a thioredoxin peroxidase with better hydrolysis activity towards H2O2 than t-BOOH. Additionally, TrGPx showed optimal pH range and half-life at 80 degrees Celsius.