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首页> 外文期刊>Biochemistry >Unprecedented Peroxidase-like Activity of Rhodnius prolixus Nitrophorin 2: Identification of the [FeIV═O Por•]+ and [FeIV═O Por](Tyr38•) Intermediates and Their Role(s) in Substrate Oxidation
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Unprecedented Peroxidase-like Activity of Rhodnius prolixus Nitrophorin 2: Identification of the [FeIV═O Por•]+ and [FeIV═O Por](Tyr38•) Intermediates and Their Role(s) in Substrate Oxidation

机译：Rhodnius prolixus硝化蛋白的前所未有的过氧化物酶活性：[FeIV═OPor•] +和[FeIV═OPor]（Tyr38•）中间体的鉴定及其在底物氧化中的作用

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摘要

We have identified a novel enzymatic reaction for nitrophorin 2 (NP2), a heme protein previouslyncharacterized as a nitric oxide carrier in the saliva of the Rhodnius prolixus insect. NP2 exhibited levels ofnperoxidase activity comparable to those of the bifunctional peroxidases (KatGs), despite their heme pocketnstructural differences (heme ruffling, Tyr38 and Tyr85 in hydrogen bonding interactions with the propionatesnin NP2). The intermediates of the peroxidase-like reaction of NP2 were identified by Electron ParamagneticnResonance (EPR) and electronic absorption spectroscopies. The EPRspectrumconsistent with an [FenIVdOPorn•n]nþnspecies was detected at pH <7. At pH g7, the change from a strong to a weak antiferromagnetic coupl-ning interaction for the [FenIVdOPorn•n]nþ species was accompanied by the subsequent formation of ann[FenIVdO Por](Tyrn•n) intermediate. Tyr38 was shown to be the unique naturally occurring radical site inNP2.nThe Y38F mutant stabilized the radical on the tyrosine in hydrogen-bonding interaction with the othernheme propionate (Tyr85). Kinetic studies using stopped-flow electronic absorption spectrophotometrynrevealed that the [FenIVdOPorn•n]nþ species reacts with histamine and norepinephrine in a peroxidase-likenmanner. Our findings demonstrate that NP2 has pH-dependent dual function: at the acidic pH of the insectnsaliva the protein behaves as a NO carrier, and, if exposed to the higher pH of the tissues and capillaries ofnthe host, NP2 is able to bind histamine or it can efficiently inactivate norepinephrine through a peroxidase-nlike reaction, in the presence of hydrogen peroxide.Accordingly, the unprecedented peroxidase-like activitynof NP2 is concluded to be a key biological function.
机译：我们已经确定了一种新的酶促反应—氮磷蛋白2（NP2），一种以前被表征为Rhodnius prolixus昆虫唾液中一氧化氮载体的血红素蛋白。尽管它们的血红素口袋结构差异（血红素起皱，Tyr38和Tyr85与丙酸酯神经素NP2的氢键相互作用），但NP2的过氧化物酶活性水平与双功能过氧化物酶（KatGs）相当。 NP2的过氧化物酶样反应的中间体通过电子顺磁共振（EPR）和电子吸收光谱法鉴定。在pH <7时检测到与[FenIVdOPorn•n]nþn物种一致的EPR光谱。在pH g7时，[FenIVdOPorn•n]nþ物种的反铁磁耦合作用由强变弱，伴随而来的是随后的ann [FenIVdO Por]（Tyrn•n）中间体的形成。 Tyr38被证明是NP2中唯一的天然自由基位点。nY38F突变体与酪氨酸丙氨酸（Tyr85）发生氢键相互作用，稳定了酪氨酸上的自由基。使用停止流电子吸收分光光度法的动力学研究表明，[FenIVdOPorn•n]nþ物种与过氧化酶类似的酶与组胺和去甲肾上腺素反应。我们的发现表明NP2具有pH依赖性双重功能：在昆虫唾液的酸性pH下，蛋白质充当NO载体，并且，如果暴露于宿主组织和毛细血管的较高pH下，NP2能够结合组胺或在过氧化氢的存在下，它能通过类似过氧化物酶的反应有效地去甲去甲肾上腺素。因此，NP2前所未有的类似过氧化物酶的活性被认为是关键的生物学功能。

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