Infante J P, Kinsella J E
Biochim Biophys Acta. 1978 Oct 12;526(2):440-9. doi: 10.1016/0005-2744(78)90135-3.
A novel method for the determination of equilibrium constants for reversible reactions is described. The method is based on the measurement of initial velocities of isotope transfer for a given substrate-product pair of both the forward and reverse reactions as a function of the mass action of reactants. The reciprocal values of these initial velocities are plotted against the mass action ratios of reactants. The observed Keq is the abscissa of the intersection point of these reciprocal plots, i.e. the mass action ratio at which the initial velocities of isotope transfer for both the forward and reverse reaction are identical, that is, when isotope exchange is occurring. In this manner, an observed Keq of 0.2 was obtained from CTP:phosphorylcholine cytidyltransferase (CTP:cholinephosphate cytidyltransferase, EC 2.7.7.15) at 37 degrees C and pH 7.5 under physiological conditions 1.0 mM free Mg2+ and 0.15 M salt concentration. A comparison of this value with the in vivo mass action of reactants calculated from published data indicates that this reaction is rate-limiting in the rat liver (Infante, J.P. (1977) Biochem. J. 167, 847--849).
描述了一种用于测定可逆反应平衡常数的新方法。该方法基于测量给定底物 - 产物对在正向和逆向反应中同位素转移的初始速度，作为反应物质量作用的函数。将这些初始速度的倒数与反应物的质量作用比作图。观察到的Keq是这些倒数图交点的横坐标，即正向和逆向反应中同位素转移的初始速度相同时的质量作用比，也就是发生同位素交换时的质量作用比。通过这种方式，在37℃、pH 7.5、生理条件下1.0 mM游离Mg2 +和0.15 M盐浓度时，从CTP：磷酸胆碱胞苷转移酶（CTP：胆碱磷酸胞苷转移酶，EC 2.7.7.15）获得了0.2的观察到的Keq。将该值与根据已发表数据计算的体内反应物质量作用进行比较表明，该反应在大鼠肝脏中是限速反应（Infante，J.P.（1977年）《生物化学杂志》167, 847 - 849）。
