Inhibition of paraoxonase activity in human liver microsomes by exposure to EDTA, metals and mercurials
Inhibition of paraoxonase activity in human liver microsomes by exposure to EDTA, metals and mercurials
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DOI：
10.1016/s0009-2797(97)00046-x
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发表时间：
1997-08-01
影响因子：
5.1
通讯作者：
Pla, A
中科院分区：
文献类型：
--
作者：
Gonzalvo, MC;Gil, F;Pla, A
本文研究了EDTA、Mg ~（2+）、Co ~（2+）、Ba ~（2+）、La ~（3+）、Zn ~（2+）、Cu ~（2+）、Hg ~（2+）、对羟基苯甲酸汞（p-OH-MB）和醋酸苯汞（PMA）对人肝微粒体对氧磷水解酶（paraoxonase）活性的体外抑制作用。酶活性完全抑制1 mM EDTA在一个时间依赖性的方式，在大鼠肝脏中检测到的EDTA耐药部分之前获得的数据相反。在这些结果的死后变化的可能影响检查在一个平行的实验中使用大鼠肝脏与不同的死后间隔。从我们的研究结果来看，人体肝脏中存在的EDTA耐药组分不能被排除。Ba、La和PMA表现为即刻抑制作用。相比之下，测试的其他化合物是时间依赖性抑制剂。Ba和Zn显示出最高的IC 50值。铜和汞（Hg，p-OH-MB，PMA）是人肝对氧磷酶最强的抑制剂。动力学分析（Lineweaver-Burk和狄克逊图）表明，不同的抑制剂表现出不同的抑制模式：竞争性（EDTA、Ba、La、Cu、p-OH-MB和PMA）、非竞争性（Zn）和混合性（Hg）。用二硫苏糖醇（DTT）预处理样品可防止汞剂的抑制作用。此外，汞剂抑制后，DTT恢复活性。这些结果证实了必不可少的作用-SH基团，以保持对氧磷酶的催化活性，并建议存在两种类型的-SH基团，可以在他们的本地化不同。(C)1997 Elsevier Science爱尔兰有限公司
Inhibition of paraoxon hydrolase (paraoxonase) activity by 'in vitro' exposure to EDTA, Mg2+, Co2+, Ba2+, La3+, Zn2+, Cu2+, Hg2+, p-hydroxymercuribenzoate (p-OH-MB) and phenyl mercuric acetate (PMA) was investigated in human liver microsomes. Enzyme activity was totally inhibited by 1 mM EDTA in a time-dependent manner, in contrast to previous data obtained in rat liver where an EDTA-resistant fraction was detected. The possible influence of postmortem changes in these results was checked in a parallel experiment using rat livers with different postmortem intervals. From our results the existence in human liver of an EDTA-resistant fraction cannot be discarded. Ba, La and PMA showed immediate inhibition. By contrast the other compounds tested were time-dependent inhibitors. Ba and Zn showed the highest IC50 values. Cu and mercurials (Hg, p-OH-MB, PMA) were the most potent inhibitors of human liver paraoxonase. Kinetic analysis (Lineweaver-Burk and Dixon plots) indicated that different inhibitors exhibit different inhibition patterns: competitive (EDTA, Ba, La, Cu, p-OH-MB and PMA), non competitive (Zn) and mixed (Hg). The pretreatment of sample with dithiothreitol (DTT) protects against the inhibitory effect of mercurials. Furthermore after inhibition by mercurials the activity was restored by DTT. These results confirmed the essential role of the -SH groups to maintain the catalytic activity of paraoxonase and suggest the existence of two types of -SH groups that could differ in their localization. (C) 1997 Elsevier Science Ireland Ltd.