Vishnevskaia Z I, Lobyshev V I
Biofizika. 1979 May-Jun;24(3):426-30.
The rate of enzymic reaction of ATP, ITP, GTP with myosin is studied in the presence of potassiu, ammonium and calcium ions in H2O--D2O solutions. There is no kinetic isotope effect of ITPase and GTPase reaction in the neutral pH region (VHVD = 1). The value VH/VD for the ATPase reaction in the pH range from 6.5 to 8.5 with all cations studied varies from 1.05 to 1.26. Such changes of myosin enzymic activity in D2O infer that small changes in the interaction of subunits is not the decisive one in the regulation of myosin ATPase. The equality of isotope effects in potassium salts and ammonium solution suggests that a specific effect of ammonium ion as a proton donor affects the ATPase reaction of myosin. The relationship between the value of isotope effect and D2O concentration in solution in non-linear. The shape of concentration curve suggests essential conformational changes of myosin during ATP hydrolysis.
在H₂O - D₂O溶液中，研究了在钾离子、铵离子和钙离子存在的情况下，ATP、ITP、GTP与肌球蛋白的酶促反应速率。在中性pH区域（VHVD = 1），ITP酶和GTP酶反应不存在动力学同位素效应。在pH值为6.5至8.5的范围内，对于所有研究的阳离子，ATP酶反应的VH/VD值在1.05至1.26之间变化。肌球蛋白酶活性在D₂O中的这种变化表明，亚基相互作用的微小变化在肌球蛋白ATP酶的调节中不是决定性因素。钾盐和铵溶液中同位素效应的相等表明，铵离子作为质子供体的特定效应会影响肌球蛋白的ATP酶反应。同位素效应值与溶液中D₂O浓度之间的关系是非线性的。浓度曲线的形状表明，在ATP水解过程中肌球蛋白发生了基本的构象变化。
