从摇摆背病羊的大脑中分离到的细胞色素-c氧化酶表现出不寻常的结构和不寻常的动力学。

T Alleyne, J Joseph, A Lalla, V Sampson, A Adogwa
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引用次数: 20

摘要

驼背病是羔羊的一种神经退行性疾病,而门克斯病是人类的同类疾病,它们都是由饮食中缺乏铜引起的。低酶活性的报告表明,几种含铜酶,包括细胞色素c氧化酶(COX),可能影响这些疾病的进展。为了研究其在神经退行性疾病,特别是摇摆病的发展中的作用,我们从摇摆病羔羊的大脑和肝脏中分离出COX。比较十二烷基硫酸钠聚丙烯酰胺凝胶电泳(SDS-PAGE)结合密度分析显示,患病动物肝脏COX结构正常,而相应的脑酶则缺乏II-、III-和iv亚基;缺乏率分别为55%、30%和65%。用极谱法比较了正常羔羊和病羔羊在低离子强度下肝脏和脑COX的活性。而酶从正常的大脑和两种形式的肝酶产生两相的特征Eadie-Hofstee情节,患病动物的大脑酶表现出单相K (m)为4.7 + / - 2.4 x 10 (6) m:考克斯的K (m)值正常大脑的12 + / - 2.5 x 10(6)和5.5 + / - 0.5 x 10 (7) m .我们认为改变酶结构占不典型的动力学和低活动我们发现孤立大脑酶。我们还得出结论,酶结构的改变部分解释了氧化酶活性低和ATP合成减少的原因,这已被广泛报道为摇摆背病动物的脑组织。我们假设亚基缺乏可能是由于亚基与膜之间的交联不完全造成的,并预测类似的结构和动力学因素也可能是门克斯病中COX活性低的原因。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Cytochrome-c oxidase isolated from the brain of swayback-diseased sheep displays unusual structure and uncharacteristic kinetics.

Swayback disease, a neurodegenerative disorder of lambs, and Menkes disease, the human equivalent, are caused by a deficiency of dietary copper. Reports of low enzymic activity suggest that several copper-containing enzymes, including cytochrome-c oxidase (COX), may influence the progress of these diseases. To investigate its role in the development of neurodegenerative disorders, in particular swayback disease, we isolated COX from the brains and livers of swayback-diseased lambs. Comparative sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) combined with densitometric analysis revealed that whereas the structure of COX from the liver of diseased animals was normal, the corresponding brain enzyme was subunits II-, III-, and IV-deficient; the deficiency was 55, 30, and 65% respectively. The activities of liver and brain COX from normal and diseased lambs were compared by polarographic assay at low ionic strength. Whereas the enzyme from normal brains and both forms of the liver enzyme yielded characteristic biphasic Eadie-Hofstee plots, the brain enzyme from diseased animals displayed a single phase with a K(m) of 4.7 +/- 2.4 x 10(-6) M: the K(m) values of COX from the normal brain were 12 +/- 2.5 x 10(-6) and 5.5 +/- 0.5 x 10(-7) M. We conclude that the altered enzyme structure accounts for the uncharacteristic kinetics and low activity we have observed for the isolated brain enzyme. We also conclude that the altered enzyme structure partly accounts for the low oxidase activity and decreased ATP synthesis that has been widely reported for brain tissue from swayback-diseased animals. We postulate that the subunit deficiency probably results from incomplete crosslinking between the subunits and the membrane, and predict that similar structural and kinetic factors may also account for low COX activity in Menkes disease.

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