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克氏锥虫血红素过氧化物酶的晶体结构及其底物特异性和化合物 I 中间产物的表征。

Crystal structure of Trypanosoma cruzi heme peroxidase and characterization of its substrate specificity and compound I intermediate.

机构信息

School of Chemistry, University of Bristol, Bristol, United Kingdom.

Departamento de Bioquímica, Facultad of Medicina, Universidad de la República, Montevideo, Uruguay; Centro de Investigaciones Biomédicas (CEINBIO), Facultad de Medicina, Universidad de la República, Montevideo, Uruguay.

出版信息

J Biol Chem. 2022 Aug;298(8):102204. doi: 10.1016/j.jbc.2022.102204. Epub 2022 Jun 27.

Abstract

The protozoan parasite Trypanosoma cruzi is the causative agent of American trypanosomiasis, otherwise known as Chagas disease. To survive in the host, the T. cruzi parasite needs antioxidant defense systems. One of these is a hybrid heme peroxidase, the T. cruzi ascorbate peroxidase-cytochrome c peroxidase enzyme (TcAPx-CcP). TcAPx-CcP has high sequence identity to members of the class I peroxidase family, notably ascorbate peroxidase (APX) and cytochrome c peroxidase (CcP), as well as a mitochondrial peroxidase from Leishmania major (LmP). The aim of this work was to solve the structure and examine the reactivity of the TcAPx-CcP enzyme. Low temperature electron paramagnetic resonance spectra support the formation of an exchange-coupled [Fe(IV)=O Trp] compound I radical species, analogous to that used in CcP and LmP. We demonstrate that TcAPx-CcP is similar in overall structure to APX and CcP, but there are differences in the substrate-binding regions. Furthermore, the electron transfer pathway from cytochrome c to the heme in CcP and LmP is preserved in the TcAPx-CcP structure. Integration of steady state kinetic experiments, molecular dynamic simulations, and bioinformatic analyses indicates that TcAPx-CcP preferentially oxidizes cytochrome c but is still competent for oxidization of ascorbate. The results reveal that TcAPx-CcP is a credible cytochrome c peroxidase, which can also bind and use ascorbate in host cells, where concentrations are in the millimolar range. Thus, kinetically and functionally TcAPx-CcP can be considered a hybrid peroxidase.

摘要

原生动物寄生虫克氏锥虫是引起美洲锥虫病的病原体,也称为恰加斯病。为了在宿主体内存活,T. cruzi 寄生虫需要抗氧化防御系统。其中之一是一种混合血红素过氧化物酶,即 T. cruzi 抗坏血酸过氧化物酶-细胞色素 c 过氧化物酶酶(TcAPx-CcP)。TcAPx-CcP 与 I 类过氧化物酶家族的成员具有高度的序列同一性,特别是抗坏血酸过氧化物酶(APX)和细胞色素 c 过氧化物酶(CcP),以及来自利什曼原虫的线粒体过氧化物酶(LmP)。这项工作的目的是解决 TcAPx-CcP 酶的结构并研究其反应性。低温电子顺磁共振光谱支持形成一种交换偶联的 [Fe(IV)=O Trp] 化合物 I 自由基物种,类似于 CcP 和 LmP 中使用的化合物 I 自由基物种。我们证明 TcAPx-CcP 的整体结构与 APX 和 CcP 相似,但在底物结合区域存在差异。此外,CcP 和 LmP 中从细胞色素 c 到血红素的电子转移途径在 TcAPx-CcP 结构中得以保留。稳态动力学实验、分子动力学模拟和生物信息学分析的综合表明,TcAPx-CcP 优先氧化细胞色素 c,但仍能够氧化抗坏血酸。结果表明,TcAPx-CcP 是一种可信的细胞色素 c 过氧化物酶,它也可以结合并在宿主细胞中使用抗坏血酸,其中浓度在毫摩尔范围内。因此,从动力学和功能上考虑,TcAPx-CcP 可以被视为一种混合过氧化物酶。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/ca29/9358470/0ea88fede75c/gr1.jpg

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