The effects of different magnesium and zinc isotopes on the enzyme activity of myosin subfragment-1 have been explored. The rate of the enzymatic ATP hydrolysis in reaction media enriched with the magnetic isotope, 25Mg, is twice as high as it is in reaction media enriched with the nonmagnetic isotopes, 24Mg or 26Mg. A similar effect of nuclear spin catalysis has been detected in the experiments with zinc isotopes as cofactors of the enzyme. The rate of the enzymatic ATP hydrolysis with magnetic 67Zn increases by 40–50% compared to that with nonmagnetic 64Zn or 68Zn. The magnetic-isotope effects have been observed at the physiological concentration of magnesium and zinc chlorides (5 mM). The catalytic effect of the magnetic magnesium isotope 25Mg has been revealed in the experiments with Mg-dependent ATPase of myometrial plasma membranes. The magnetic-isotope effects indicate that there is a spin-selective rate-limiting step in the chemo-mechanical process driven by the “molecular motor” due to the energy of ATP hydrolysis and that nuclear spin catalysis causes acceleration of this stage. Some possible mechanisms of the nuclear spin catalysis are discussed.

中文翻译：

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分子马达驱动酶促 ATP 水解中镁和锌的磁同位素效应

研究了不同镁和锌同位素对肌球蛋白亚片段 1 酶活性的影响。在富含磁性同位素 25Mg 的反应介质中，酶促 ATP 水解的速率是在富含非磁性同位素 24Mg 或 26Mg 的反应介质中的两倍。在锌同位素作为酶的辅助因子的实验中，已检测到核自旋催化的类似作用。与非磁性 64Zn 或 68Zn 相比，磁性 67Zn 的酶促 ATP 水解率增加了 40-50%。已在氯化镁和氯化锌 (5 mM) 的生理浓度下观察到磁同位素效应。磁性镁同位素 25Mg 的催化作用已在肌层细胞膜的镁依赖性 ATP 酶实验中得到揭示。磁同位素效应表明，由于 ATP 水解的能量，在“分子马达”驱动的化学机械过程中存在自旋选择性限速步骤，并且核自旋催化导致该阶段的加速。讨论了核自旋催化的一些可能机制。