Nimura E, Miura K, Shinobu L A, Imura N
Department of Public Health, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
Ecotoxicol Environ Saf. 1987 Oct;14(2):184-9. doi: 10.1016/0147-6513(87)90061-3.
The effects of Cd2+ on Ca2+-sensitive myosin ATPase activity were examined. In the absence of Ca2+, the Ca2+-dependent myosin ATPase activity was enhanced by Cd2+ to the same extent as with Ca2+ at concentrations ranging from 10(-6) to 10(-3) M. At 10(-2) M, however, no activation was observed. Zn2+, Co2+, and Sr2+ also activated the myosin ATPase. Sr2+ and Co2+ were less effective. Hg2+, Cr3+, and Cu2+ were essentially inactive. In the presence of below 10(-3) M Ca2+, the increase in the enzyme activity observed on the addition of Cd2+ was in addition to that caused by Ca2+ alone. The ability of metal ions to activate myosin ATPase was compared with that to activate calmodulin-dependent cAMP phosphodiesterase. The activating effects of the metal ions tested were in the order of Ca2+ greater than Cd2+ greater than Zn2+ greater than Co2+ greater than Sr2+ for Ca2+-sensitive myosin ATPase and Ca2+ greater than Cd2+ greater than Sr2+ greater than Zn2+ greater than Hg2+ greater than Co2+ for cAMP phosphodiesterase. Cd2+ activated both enzyme activities most efficiently among the metal ions tested except Ca2+. These results indicate that Cd2+ is able to substitute for Ca2+ in the case of Ca2+ dependent enzymes, regardless of whether or not calmodulin participates in the activating process.
研究了Cd2+对Ca2+敏感的肌球蛋白ATP酶活性的影响。在没有Ca2+的情况下，Cd2+在10(-6)至10(-3) M的浓度范围内，与Ca2+一样能同等程度地增强Ca2+依赖性肌球蛋白ATP酶活性。然而，在10(-2) M时，未观察到激活作用。Zn2+、Co2+和Sr2+也能激活肌球蛋白ATP酶。Sr2+和Co2+的效果较差。Hg2+、Cr3+和Cu2+基本无活性。在低于10(-3) M Ca2+存在的情况下，添加Cd2+时观察到的酶活性增加是在仅由Ca2+引起的增加之外的。将金属离子激活肌球蛋白ATP酶的能力与激活钙调蛋白依赖性cAMP磷酸二酯酶的能力进行了比较。对于Ca2+敏感的肌球蛋白ATP酶，所测试金属离子的激活效果顺序为Ca2+＞Cd2+＞Zn2+＞Co2+＞Sr2+；对于cAMP磷酸二酯酶，顺序为Ca2+＞Cd2+＞Sr2+＞Zn2+＞Hg2+＞Co2+。在除Ca2+之外所测试的金属离子中，Cd2+最有效地激活了这两种酶的活性。这些结果表明，在Ca2+依赖性酶的情况下，Cd2+能够替代Ca2+，无论钙调蛋白是否参与激活过程。
