Torres J C, Babul J
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago.
Eur J Biochem. 1991 Sep 1;200(2):471-6. doi: 10.1111/j.1432-1033.1991.tb16206.x.
An in vitro assay model is introduced for the coupled assay of phosphofructokinase (PFK) and fructose-bisphosphatase. The model is applied to the study of three PFK of Escherichia coli: two isoenzymes, phosphofructokinase-1 (PFK-1) and phosphofructokinase-2 (PFK-2), and a mutant form of phosphofructokinase-2 (PFK-2*). Results show that for a variety of conditions the PFK-1/fructose-bisphosphatase pair gives the lowest and the PFK-2*/fructose-bisphosphatase pair the highest rates of substrate cycle, with the PFK-2/fructose-bisphosphatase pair in an intermediate position. The effects of variables such as maximum activity ratios and MgATP concentration were explored. The possible role of MgATP in decreasing the futile cycle of the PFK-2/fructose-bisphosphatase pair is described. The results are discussed in terms of possible metabolic consequences of PFK-2* and of predictions of the model to be tested in vivo.
介绍了一种用于磷酸果糖激酶（PFK）和果糖二磷酸酶偶联测定的体外分析模型。该模型应用于对大肠杆菌三种PFK的研究：两种同工酶，即磷酸果糖激酶-1（PFK-1）和磷酸果糖激酶-2（PFK-2），以及磷酸果糖激酶-2的一种突变形式（PFK-2*）。结果表明，在多种条件下，PFK-1/果糖二磷酸酶对的底物循环速率最低，PFK-2*/果糖二磷酸酶对的底物循环速率最高，PFK-2/果糖二磷酸酶对处于中间位置。探讨了最大活性比和MgATP浓度等变量的影响。描述了MgATP在降低PFK-2/果糖二磷酸酶对无效循环中的可能作用。根据PFK-2*可能的代谢后果以及该模型在体内测试的预测对结果进行了讨论。
