Uyemura S A, Jordani M C, Polizello A C, Curti C
Department of Clinical, Toxicological and Bromatological Analysis, School of Pharmaceutical Science, University of São Paulo, Brasil.
Mol Cell Biochem. 1996 Dec 20;165(2):127-33. doi: 10.1007/BF00229474.
The kinetic properties of ATP hydrolysis and synthesis by FoF1-ATPase of heart mitochondria were evaluated during the acute phase of T. cruzi infection in rats. Mitochondria and submitochondrial particles were isolated 7 days (early stage) and 25 days (late stage) following infection of rats with 2 x 10(5) trypomastigote forms of the Y strain of T. cruzi. The kinetic properties for ATP hydrolysis were altered for the early but not the late stage, showing a changed pH profile, increased K0.5 values, and a decreased total Vmax. The Arrhenius' plot for membrane-associated enzyme showed a higher transition temperature with a lower value for the activation energy in body temperature. For the Triton X-100-solubilized enzyme, the plot was similar to the control. A decrease in the efficiency of ADP phosphorylation by mitochondria, measured by the firefly-luciferase luminescence, was observed only during the late stage and appeared to be correlated with a decrease in the affinity of the FoF1-ATPase for ADP. It is proposed that in the early stage, during the acute phase of T. cruzi infection in rats, heart FoF1-ATPase undergoes a membrane-dependent conformational change in order to maintain the phosphorylation potential of mitochondria, which would compensate for the uncoupling of mitochondrial function. Also, during both the early and late stages, the enzyme seems to be under the regulation of the endogenous inhibitor protein for the preservation of cellular ATP levels.
在大鼠克氏锥虫感染急性期，对心脏线粒体F₀F₁ - ATP酶水解和合成ATP的动力学特性进行了评估。用2×10⁵个克氏锥虫Y株的锥鞭毛体形式感染大鼠后7天（早期）和25天（晚期）分离线粒体和亚线粒体颗粒。ATP水解的动力学特性在早期发生改变，晚期未改变，表现为pH曲线改变、K₀.₅值增加和总Vmax降低。膜相关酶的阿累尼乌斯图显示，在体温下转变温度较高，活化能值较低。对于Triton X - 100增溶的酶，该图与对照相似。仅在晚期观察到通过萤火虫荧光素酶发光测量的线粒体ADP磷酸化效率降低，这似乎与F₀F₁ - ATP酶对ADP的亲和力降低有关。有人提出，在大鼠克氏锥虫感染急性期的早期，心脏F₀F₁ - ATP酶会发生膜依赖性构象变化，以维持线粒体的磷酸化电位，这将补偿线粒体功能的解偶联。此外，在早期和晚期，该酶似乎都受内源性抑制蛋白的调节，以维持细胞ATP水平。
