Russell T R, Thompson W J, Schneider F W, Appleman M M
Proc Natl Acad Sci U S A. 1972 Jul;69(7):1791-5. doi: 10.1073/pnas.69.7.1791.
Kinetic and chromatographic analysis of cyclic nucleotide phosphodiesterase (EC 3.1.4.c) obtained from rat tissue has revealed that this enzyme exists in at least two molecular forms. After chromatographic separation, one form (cyclic AMP phosphodiesterase) still exhibits kinetics suggestive of the action of either two enzymes or one enzyme under negative cooperative regulation. Computer model studies were undertaken to distinguish between these two possibilities. The matrix method was used to generate the partition functions for (a) the sum of two independent enzymes and (b) one enzyme exhibiting negative cooperative kinetics. The experimental data were fitted to the theoretical models by a nonlinear least-squares computer program. The results show that, while both models can fit the data, the two-enzyme model would require contamination far in excess of what is detectable physically or by activity measurements. Thus, the negative cooperative model seems the more appropriate theoretical explanation of the observed kinetic behavior of this enzyme. The implication of negative cooperativity with respect to the regulation of cyclic AMP concentrations in physiological systems is discussed.
对从大鼠组织中获得的环核苷酸磷酸二酯酶（EC 3.1.4.c）进行的动力学和色谱分析表明，该酶至少以两种分子形式存在。色谱分离后，一种形式（环磷酸腺苷磷酸二酯酶）的动力学仍表明可能是两种酶的作用，或者是一种处于负协同调节下的酶的作用。进行了计算机模型研究以区分这两种可能性。采用矩阵法生成了（a）两种独立酶之和以及（b）表现出负协同动力学的一种酶的分配函数。通过非线性最小二乘计算机程序将实验数据拟合到理论模型中。结果表明，虽然两种模型都能拟合数据，但双酶模型所需的污染远远超过通过物理检测或活性测量所能检测到的程度。因此，负协同模型似乎是对该酶观察到的动力学行为更合适的理论解释。文中讨论了负协同性对生理系统中环磷酸腺苷浓度调节的影响。
