Mas-Oliva J
Departamento de Bioenergética, Universidad Nacional Autónoma de México, D.F.
Mol Cell Biochem. 1989 Aug 15;89(1):87-93. doi: 10.1007/BF00228283.
I have investigated the effect of lead on the erythrocyte ghosts (Ca2+,Mg2+)-ATPase, with special attention to the role of calmodulin in this phenomena. Under regular incubation conditions, lead inhibits the enzyme with an IC50 of 6.0 microM. The presence of exogenously added calmodulin apparently does not change this inhibitory value. DTT added during the incubation period does not affect the inhibitory action of lead. However, when the membranes are preincubated with DTT, an important IC50 displacement is observed, either with or without added calmodulin. Since [125I]calmodulin binding to the membranes is enhanced when lead is used, the possibility of a lead/calmodulin complex that optimally stimulates the enzyme using lead concentrations between 1.0 and 10.0 microM, is suggested. Based on the experimental data, I propose two well defined actions of lead; first, an inhibitory action upon the ATPase above 1.0 microM lead, most probably related to essential sulphydryl groups in the enzyme; and second, a direct action of lead upon calmodulin at lead concentrations below 1.0 microM.
我研究了铅对红细胞血影（Ca2 +，Mg2 +）-ATP酶的影响，特别关注钙调蛋白在这一现象中的作用。在常规孵育条件下，铅抑制该酶，IC50为6.0微摩尔。外源添加钙调蛋白的存在显然不会改变这一抑制值。孵育期间添加二硫苏糖醇（DTT）不影响铅的抑制作用。然而，当膜与DTT预孵育时，无论是否添加钙调蛋白，都会观察到重要的IC50位移。由于使用铅时[125I]钙调蛋白与膜的结合增强，因此提出了一种铅/钙调蛋白复合物的可能性，该复合物在1.0至10.0微摩尔的铅浓度下能最佳地刺激该酶。基于实验数据，我提出铅有两种明确的作用；第一，在铅浓度高于1.0微摩尔时对ATP酶的抑制作用，很可能与该酶中的必需巯基有关；第二，在铅浓度低于1.0微摩尔时铅对钙调蛋白的直接作用。
