Whitehead E P, Nucci R, Vaccaro C, Rossi M
Department of Biochemical Sciences, University of Rome, Italy.
Arch Biochem Biophys. 1991 Aug 15;289(1):12-8. doi: 10.1016/0003-9861(91)90435-l.
The ratio of the steady-state kinetic Hill coefficients of two different effectors equals (under some rather weak general assumptions) the ratio in which the effectors displace each other from an enzyme. This principle can make implications of experimental allosteric enzyme kinetic data immediately apparent. We can use it to find that one molecule of the allosteric inhibitor of dCMP aminohydrolase, at moderately high effector concentrations, displaces one molecule of substrate, or one molecule of activator, whereas at very high concentrations, one molecule of inhibitor displaces two of substrate. Further use of the principle suggests that substrate, at high concentrations, binds binds to activator sites. However, ratios of substrate, activator, and inhibitor Hill coefficients are incompatible with a simple model of activation in which substrate and activator are bound to the same conformation.
两种不同效应物的稳态动力学希尔系数之比（在一些相当弱的一般假设下）等于效应物从酶上相互取代的比例。这一原理可以使实验性变构酶动力学数据的含义立即变得明显。我们可以用它来发现，在适度高的效应物浓度下，一分子dCMP氨基水解酶的变构抑制剂取代一分子底物或一分子激活剂，而在非常高的浓度下，一分子抑制剂取代两分子底物。对该原理的进一步应用表明，在高浓度下，底物会结合到激活剂位点。然而，底物、激活剂和抑制剂的希尔系数之比与底物和激活剂结合到相同构象的简单激活模型不相符。
