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首页> 外文期刊>Biochemistry >Eukaryotic Catalase-Peroxidase: The Role of the Trp-Tyr-Met Adduct in Protein Stability, Substrate Accessibility, and Catalysis of Hydrogen Peroxide Dismutation
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Eukaryotic Catalase-Peroxidase: The Role of the Trp-Tyr-Met Adduct in Protein Stability, Substrate Accessibility, and Catalysis of Hydrogen Peroxide Dismutation

机译：真核过氧化氢酶过氧化物酶：Trp-Tyr-Met加合物在蛋白质稳定性，底物可及性和过氧化氢歧化催化中的作用

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摘要

Recently, it was demonstrated that bifunctional catalase-peroiddases (KatGs) are found not only in archaea and bacteria but also in lower eukaryotes. Structural studies and preliminary biochemical data of the secreted KatG from the rice pathogen Magnaporthe grisea (MagKatG2) suggested both similar and novel features when compared to those of the prokaryotic counterparts studied so far. In this work, we demonstrate the role of the autocatalytically formed redox-active Trp140-Tyr273-Met299 adduct of MagKatG2 in (i) the maintenance of the active site architecture, (ii) the catalysis of hydrogen peroxide dismutation, and (iii) the protein stability by comparing wild-type MagKatG2 with the single mutants Trp140Phe, Tyr273Phe, and Met299Ala. The impact of disruption of the covalent bonds between the adduct residues on the spectral signatures and heme cavity architecture was small. By contrast, loss of its integrity converts bifunctional MagKatG2 to a monofunctiona1 peroxidase of significantly reduced thermal stability. It increases the accessibility of ligands due to the increased flexibility of the KatG-typical large loop 1 (LL1), which contributes to the substrate access channel and anchors at the adduct Tyr. We discuss these data with respect to those known from prokaryotic KatGs and in addition present a high-resolution structure of an oxoiron compound of MagKatG2.
机译：最近，已证明双功能过氧化氢酶-过氧化物酶（KatGs）不仅在古细菌和细菌中发现，而且在低等真核生物中也发现。与迄今研究的原核生物相比，水稻病原体稻瘟病菌Magnaathe（MagKatG2）分泌的KatG的结构研究和初步生化数据显示出相似和新颖的特征。在这项工作中，我们证明了MagKatG2的自催化形成的氧化还原活性Trp140-Tyr273-Met299加合物在以下方面的作用：（i）维持活性位点结构，（ii）催化过氧化氢歧化，以及（iii）通过比较野生型MagKatG2与单个突变体Trp140Phe，Tyr273Phe和Met299Ala的蛋白质稳定性。加合物残基之间的共价键的破坏对光谱特征和血红素腔结构的影响很小。相反，丧失其完整性会将双功能MagKatG2转换为热稳定性大大降低的单功能过氧化物酶。由于增加了KatG型大环1（LL1）的灵活性，它增加了配体的可及性，这有助于底物进入通道和锚定在加合物Tyr上。我们讨论这些数据相对于从原核生物KatGs已知的数据，此外还提出了MagKatG2的含氧铁化合物的高分辨率结构。

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