Inoue A, Fukushima Y, Tonomura Y
J Biochem. 1975 Dec;78(6):1113-21. doi: 10.1093/oxfordjournals.jbchem.a131007.
The effects of D2O on the elementary steps in the contractile and transport ATPase [EC 3.6.1.3] reactions were studied, and the following results were obtained: 1. The rate of H-meromyosin ATPase in the steady state decreased in D2O to 60% of that in H2O. Deuterium oxide did not affect the size or rate of the initial burst of Pi liberation, i.e. the amount or rate of formation of the reactive myosin-phosphate-ADP complex, MADPP. Moreover, neither the rate of change in the fluorescence spectrum of H-meromyosin induced by ATP (the rate of formation of the second enzyme-ATP complex, M2ATP) nor the rate constant of decomposition of MADPP into M degrees + ADP + Pi was affected by D2O. However, the equilibrium constant of the step M2ATP in equilibrium MADPP decreased in D2O to about 1/2 the value in H2O. 2. In the case of the Na+-K+-dependent ATPase reactin, neither the rate constant of formation of the second enzyme-ATP complex, E2ATP, nor that of decomposition of a phosphorylated intermediate, EADP approximately P, was affected by D2O. However, the equilibrium constant of the step E2ATP in equilibrium EADP approximately P decreased in D2O to about 1/2.5-1/4 of the value in H2O. These results suggest a similarity between the modes of binding of phosphate in MADPP in the myosin ATPase reaction and in EADP approximatley P in the Na+-K+-dependent ATPase reaction.
研究了重水（D₂O）对收缩和转运ATP酶[EC 3.6.1.3]反应中基本步骤的影响，得到以下结果：1. 稳态下H-肌球蛋白ATP酶的速率在D₂O中降至H₂O中的60%。氧化氘不影响Pi释放初始爆发的大小或速率，即反应性肌球蛋白-磷酸-ADP复合物（MADPP）的形成量或速率。此外，ATP诱导的H-肌球蛋白荧光光谱变化速率（第二种酶-ATP复合物M₂ATP的形成速率）以及MADPP分解为M⁰ + ADP + Pi的速率常数均不受D₂O影响。然而，M₂ATP在平衡态MADPP中的平衡常数在D₂O中降至H₂O中值的约1/2。2. 在Na⁺-K⁺依赖性ATP酶反应中，第二种酶-ATP复合物E₂ATP的形成速率常数以及磷酸化中间体EADP≈P的分解速率常数均不受D₂O影响。然而，E₂ATP在平衡态EADP≈P中的平衡常数在D₂O中降至H₂O中值的约1/2.5 - 1/4。这些结果表明，肌球蛋白ATP酶反应中MADPP的磷酸结合模式与Na⁺-K⁺依赖性ATP酶反应中EADP≈P的磷酸结合模式相似。
