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首页> 外文期刊>Journal of applied toxicology >Carboxylesterase: specificity and spontaneous reactivation of an endogenous scavenger for organophosphorus compounds.
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Carboxylesterase: specificity and spontaneous reactivation of an endogenous scavenger for organophosphorus compounds.

机译：羧酸酯酶：有机磷化合物的内源性清除剂的特异性和自发活化。

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摘要

The ability of carboxylesterase (CaE) to act as a bioscavenger to provide protection against organophosphorus (OP) compounds has been demonstrated in several animal models. To further evaluate the effectiveness of CaE as a bioscavenger, the specificity and stoichiometry of the detoxication of OP compounds by rat plasma CaE were examined. The specificity of CaE was evaluated by determining the bimolecular rate constants for inhibition (k(i)) of CaE by a variety of OP compounds. CaE exhibited a broad specificity for neutral OP compounds with k(i) > 10(6) M(-1) x min(-1) for paraoxon, sarin, soman, diisopropyl fluorophosphate, and diphenyl p-nitrophenyl phosphinate. CaE exhibited poor reactivity (k(i) < 10(4) M(-1) x min(-1)) with cationic OP compounds, such as echothiophate, VX, and iso-OMPA. The stoichiometry of CaE detoxication of OP compounds was evaluated by determining the rates of enzyme reactivation and ageing of OP-inhibited CaE. CaE exhibited no ageing after inhibition by any of the OP compounds, including soman. However, OP-inhibited CaE did exhibit spontaneous reactivation with reactivation rates that decreased as the size of the OP increased (i.e., VX > sarin > soman). The pH dependence of the spontaneous reactivation of sarin-inhibited CaE suggested that its reactivation was dependent on an amino acid residue with a pK(a) of 6.1, which is probably a histidine that is highly conserved in CaE but not in other esterases. Copyright 2001 John Wiley & Sons, Ltd.
机译：几种动物模型已经证明了羧酸酯酶（CaE）充当生物清除剂以提供针对有机磷（OP）化合物的保护的能力。为了进一步评估CaE作为生物清除剂的有效性，研究了大鼠血浆CaE对OP化合物解毒的特异性和化学计量。通过确定各种OP化合物对CaE的抑制作用（k（i））的双分子速率常数，可以评估CaE的特异性。 CaE对对氧磷，沙林，梭曼，氟代磷酸二异丙酯和对硝基苯基次膦酸二苯基酯的k（i）> 10（6）M（-1）x min（-1）的中性OP化合物表现出广泛的特异性。 CaE与阳离子OP化合物（例如，硫代硫酸盐，VX和iso-OMPA）的反应性较差（k（i）<10（4）M（-1）x min（-1））。通过确定酶的再活化速率和OP抑制的CaE的衰老来评估OP化合物CaE脱毒的化学计量。在被任何梭菌化合物（包括梭曼）抑制后，CaE均未表现出老化。但是，OP抑制的CaE确实表现出自发的激活，其激活率随OP大小的增加而降低（即VX>沙林>梭曼）。沙林抑制的CaE的自发激活的pH依赖性表明其激活依赖于pK（a）为6.1的氨基酸残基，这可能是一个在CaE中高度保守但在其他酯酶中高度保守的组氨酸。版权所有2001 John Wiley＆Sons，Ltd.

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