Studies on the extra-mitochondrial CoA-ester formation of valproic and Δ4-valproic acids
Studies on the extra-mitochondrial CoA-ester formation of valproic and Δ4-valproic acids
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DOI：
10.1016/j.bbalip.2007.01.010
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发表时间：
2007-04-01
影响因子：
4.8
通讯作者：
Silva, Margarida F. B.
中科院分区：
文献类型：
--
作者：
Aires, Catia C. P.;Ruiter, Jos P. N.;Silva, Margarida F. B.
研究了丙戊酸（VPA）及其主要微粒体代谢产物δ（4）-丙戊酸是否可在细胞胞质溶胶中活化为相应CoA酯的假设。通过VPA处理大鼠肝匀浆差速离心（离体研究）和VPA和辅因子孵育大鼠肝细胞毛地黄皂苷分级分离（体外研究）获得不同亚细胞级分，测定丙戊酸辅酶A形成。结果表明，VPA激活可能发生在细胞质中，并不局限于线粒体基质，直到现在认为。此外，在体外证实了Delta（4）-VPA的活化。在体外孵育后检测到丙戊酰辅酶A和δ（4）-丙戊酰辅酶A，前者也存在于处理大鼠肝细胞的线粒体和胞质组分中。在细胞溶质组分中表征了对丙戊酸-CoA的活化，相对于时间和蛋白质进行了优化，并估计了反应底物的动力学常数（Km（app））。其他中链脂肪酸减少了丙戊酸-CoA的形成，表明线粒体和线粒体外VPA活化酶的竞争。目前的研究结果表明与VPA相关的线粒体功能障碍的其他机制，它们可能有助于进一步了解与这种药物相关的毒性作用。(C)2007 Elsevier B. V.保留所有权利。
The hypothesis whether valproic acid (VPA) and its main microsomal metabolite, Delta(4) -valproic acid, can be activated to the respective CoA esters in the cell cytosol was investigated. The valproyl-CoA formation was measured in different subcellular fractions obtained by differential centrifugation of liver homogenates of rats treated with VPA (studies ex vivo) and digitonin fractionation of rat hepatocytes incubated with VPA and cofactors (studies in vitro). The results show that VPA activation may occur in the cytosol and is not restricted to the mitochondrial matrix as believed until now. Furthermore, the activation of Delta(4)-VPA is demonstrated in vitro. Valproyl-CoA and Delta(4)-valproyl-CoA were detected after in vitro incubations and the former also in the mitochondrial and cytosolic fractions obtained from liver cells of treated rats. The activation to valproyl-CoA was characterized in cytosolic fractions, optimized with respect to time and protein and the kinetic constants (K-m(app)) were estimated for the reaction substrates. Other medium-chain fatty acids decreased the formation of valproyl-CoA suggesting a competition for both mitochondrial and extramitochondrial VPA activating enzymes. The present findings suggest additional mechanisms of mitochondrial dysfunction associated with VPA, and they may contribute to the further understanding of the toxic effects associated with this drug. (C) 2007 Elsevier B.V. All rights reserved.