Redox thermodynamics of lactoperoxidase and eosinophil peroxidase
Redox thermodynamics of lactoperoxidase and eosinophil peroxidase
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DOI：
10.1016/j.abb.2009.11.021
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发表时间：
2010-02-01
影响因子：
3.9
通讯作者：
Obinger, Christian
中科院分区：
文献类型：
--
作者：
Battistuzzi, Gianantonio;Bellei, Marzia;Obinger, Christian
嗜酸性粒细胞过氧化物酶（EPO）和乳过氧化物酶（LPO）是哺乳动物先天免疫系统的重要组成部分。这些血红素酶属于过氧化物酶-环氧合酶超家族，催化硫氰酸盐、溴化物和亚硝酸盐氧化为对入侵病原体有毒的次硫氰酸盐、次溴酸和二氧化氮。为了更好地了解观察到的与血红素和蛋白质结构相关的底物特异性和氧化能力的差异，进行了全面的光谱电化学研究。 EPO和LPO的Fe(III)/Fe(II)对的还原电位(E-or)分别测定为-126 mV和-176 mV(25℃，pH 7.0)。变温实验表明EPO和LPO具有不同的还原热力学特征。特别是，铁 EPO 的还原在热函和熵方面是不利的，而在 LPO 中，选择性稳定氧化形式的熵项在有利于 Fe(III) 还原的函项上占优势。这些数据是关于血红素腔和基质通道的结构进行讨论的。与已发表的髓过氧化物酶数据的比较表明，血红素对蛋白质连接和血红素扭曲油、哺乳动物过氧化物酶的氧化还原化学的影响，以及对这些生理上重要的氧化还原酶的酶性质的影响。 (C) 2009 Elsevier Inc. 保留所有权利。
Eosinophil peroxidase (EPO) and lactoperoxidase (LPO) are important constituents of the innate immune system of mammals. These heme enzymes belong to the peroxidase-cyclooxygenase superfamily and catalyze the oxidation of thiocyanate, bromide and nitrite to hypothiocyanate, hypobromous acid and nitrogen dioxide that are toxic for invading pathogens. in order to gain a better understanding of the observed differences in Substrate specificity and oxidation capacity in relation to heme and protein structure, a comprehensive spectro-electrochemical investigation was performed. The reduction potential (E-or) of the Fe(III)/Fe(II) Couple of EPO and LPO was determined to be -126 mV and -176 mV, respectively (25 degrees C, pH 7.0). Variable temperature experiments show that EPO and LPO feature different reduction thermodynamics. In particular, reduction of ferric EPO is enthalpically and entropically disfavored, whereas in LPO the entropic term, which selectively stabilizes the oxidized form, prevails on the enthalpic term that favors reduction of Fe(III). The data are discussed with respect to the architecture of the heme cavity and the substrate channel. Comparison with published data for myeloperoxidase demonstrates the effect of heme to protein linkages and heme distortion oil the redox chemistry of mammalian peroxidases and in consequence on the enzymatic properties of these physiologically important oxidoreductases. (C) 2009 Elsevier Inc. All rights reserved.