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( 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.
( Zhongmei Liu ),( Zhongyi Cheng ),( Shuangshuang Ye ),( Li Zhou ),( Zhemin Zhou ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.9
Phenylalanine hydroxylase from Chromobacterium violaceum (CvPAH) is a monomeric enzyme that converts phenylalanine to tyrosine. It shares high amino acid identity and similar structure with a subunit of human phenylalanine hydroxylase that is a tetramer, resulting in the latent application in medications. In this study, semirational design was applied to CvPAH to improve the catalytic ability based on molecular dynamics simulation analyses. Four Nterminal truncated variants and one single point variant were constructed and characterized. The D267P variant showed a 2.1-fold increased thermal stability compared to the wild type, but lower specific activity was noted compared with the wild type. The specific activity of all truncated variants was a greater than 25% increase compared to the wild type, and these variants showed similar or slightly decreased thermostability with the exception of the N-Δ9 variant. Notably, the N-Δ9 variant exhibited a 1.2-fold increased specific activity, a 1.3-fold increased thermostability and considerably increased catalytic activity under the neutral environment compared with the wild type. These properties of the N-Δ9 variant could advance medical and pharmaceutical applications of CvPAH. Our findings indicate that the N-terminus might modulate substrate binding, and are directives for further modification and functional research of PAH and other enzymes.