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( Yao Zhou ),( Shengmin Zhou ),( Haijun Yu ),( Jingyi Li ),( Yang Xia ),( Baoyi Li ),( Xiaoli Wang ),( Ping Wang ) 한국미생물 · 생명공학회 2016 Journal of microbiology and biotechnology Vol.26 No.5
S-Nitrosoglutathione reductase (GSNOR) metabolizes S-nitrosoglutathione (GSNO) and has been shown to play important roles in regulating cellular signaling and formulating host defense by modulating intracellular nitric oxide levels. The enzyme has been found in bacterial, yeast, mushroom, plant, and mammalian cells. However, to date, there is still no evidence of its occurrence in filamentous fungi. In this study, we cloned and investigated a GSNOR-like enzyme from the filamentous fungus Aspergillus nidulans. The enzyme occurred in native form as a homodimer and exhibited low thermal stability. GSNO was an ideal substrate for the enzyme. The apparent Km and kcat values were 0.55 mM and 34,100 min-1, respectively. Substrate binding sites and catalytic center amino acid residues based on those from known GSNORs were conserved in this enzyme, and the corresponding roles were verified using site-directed mutagenesis. Therefore, we demonstrated the presence of GSNOR in a filamentous fungus for the first time.
( Yang Xia ),( Haijun Yu ),( Zhemin Zhou ),( Naoki Takaya ),( Shengmin Zhou ),( Ping Wang ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.1
Most eukaryotic peroxiredoxins (Prxs) are readily inactivated by a high concentration of hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) during catalysis owing to their “GGLG” and “YF” motifs. However, such oxidative stress sensitive motifs were not found in the previously identified filamentous fungal Prxs. Additionally, the information on filamentous fungal Prxs is limited and fragmentary. Herein, we cloned and gained insight into Aspergillus nidulans Prx (An.PrxA) in the aspects of protein properties, catalysis characteristics, and especially H<sub>2</sub>O<sub>2</sub> tolerability. Our results indicated that An.PrxA belongs to the newly defined family of typical 2-Cys Prxs with a marked characteristic that the “resolving” cysteine (C<sub>R</sub>) is invertedly located preceding the “peroxidatic” cysteine (C<sub>P</sub>) in amino acid sequences. The inverted arrangement of C<sub>R</sub> and C<sub>P</sub> can only be found among some yeast, bacterial, and filamentous fungal deduced Prxs. The most surprising characteristic of An.PrxA is its extraordinary ability to resist inactivation by extremely high concentrations of H<sub>2</sub>O<sub>2</sub>, even that approaching 600 mM. By screening the H<sub>2</sub>O<sub>2</sub>-inactivation effects on the components of Prx systems, including Trx, Trx reductase (TrxR), and Prx, we ultimately determined that it is the robust filamentous fungal TrxR rather than Trx and Prx that is responsible for the extreme H<sub>2</sub>O<sub>2</sub> tolerence of the An.PrxA system. This is the first investigation on the effect of the electron donor partner in the H<sub>2</sub>O<sub>2</sub> tolerability of the Prx system.