Nowak T
J Biol Chem. 1978 Mar 25;253(6):1998-2004.
The distance between the obligatory monovalent and divalent cations at the active site of pyruvate kinase (rabbit muscle) has been used to monitor structural changes at various successive intermediates in the catalytic reaction and to relate structure and activity of substrate analogs. Determinations of distance were obtained from measurements of the longitudinal relaxation rate (1/T1) of the methyl protons of methyl ammonium ion, which was affected by the activating divalent cation Mn2+ in the various enzyme complexes. A frequency dependence of the 1/T1 effects with several complexes indicats that the observed relaxation rate changes are modulated by changes in the cation-cation distances. The results are interpreted as a sequence of structural changes at the active site which occur upon substrate binding, catalysis, and product release. Substrate analogs which are good analogs of phosphoenolpyruvate by kinetic criteria induce structural changes analogous to the substrate. An attempt is made to correlate the cation-cation distance changes to other structural changes reported for pyruvate kinase.
丙酮酸激酶（兔肌肉）活性位点处必需单价阳离子和二价阳离子之间的距离已被用于监测催化反应中各个连续中间体的结构变化，并关联底物类似物的结构与活性。距离的测定是通过测量甲基铵离子甲基质子的纵向弛豫率（1/T1）得到的，该弛豫率在各种酶复合物中受到活化二价阳离子Mn2+的影响。几种复合物的1/T1效应的频率依赖性表明，观察到的弛豫率变化是由阳离子 - 阳离子距离的变化调节的。结果被解释为活性位点处一系列的结构变化，这些变化发生在底物结合、催化和产物释放过程中。根据动力学标准，那些是磷酸烯醇丙酮酸良好类似物的底物类似物会诱导与底物类似的结构变化。人们试图将阳离子 - 阳离子距离的变化与丙酮酸激酶报道的其他结构变化相关联。
