Kuzmic P
University of Wisconsin, School of Pharmacy, Madison 53706.
Biochem Biophys Res Commun. 1993 Mar 31;191(3):998-1003. doi: 10.1006/bbrc.1993.1316.
The kinetics and thermodynamics of the monomer--dimer equilibrium for HIV-1 proteinase are investigated in a concentration jump experiment, at a concentration of the substrate that is substantially lower than the Michaelis constant. Under these conditions the substrate-induced stabilization of the active dimer is suppressed, and the integral rate equation can be obtained in a closed form. Both the monomer--dimer bimolecular association rate constant and the corresponding equilibrium dissociation constant are obtained directly by nonlinear regression analysis of the reaction time-course. In buffers of low ionic strength and in the absence of external ligands (substrates and inhibitors), the equilibrium dissociation constant at 37 degrees C is 440 +/- 52 nM, a value significantly higher than previous estimates obtained at a comparatively high concentration of substrates.
在浓度跳跃实验中，研究了HIV-1蛋白酶单体 - 二聚体平衡的动力学和热力学，实验底物浓度远低于米氏常数。在这些条件下，底物诱导的活性二聚体的稳定作用受到抑制，积分速率方程可以以封闭形式得到。单体 - 二聚体双分子缔合速率常数和相应的平衡解离常数都通过反应时间进程的非线性回归分析直接获得。在低离子强度缓冲液中且不存在外部配体（底物和抑制剂）的情况下，37摄氏度时的平衡解离常数为440±52 nM，该值显著高于先前在相对高底物浓度下获得的估计值。
