Bermudez J L, Chambers J P, Rizopoulos E, Kumar P, Valdes J J, Martinez A O
Brain Research Laboratory of Biochemistry, University of Texas, San Antonio.
Cell Calcium. 1989 May-Jun;10(4):181-7. doi: 10.1016/0143-4160(89)90001-8.
The Ca2+-stimulated, Mg2+-dependent ATPase of SV40 transformed WI38 lung fibroblast homogenates exhibits a high affinity for Ca2+ (K0.5 = 0.20 microM) and moderately high affinity for ATP (Km = 28.6 microM) and Mg2+ (K0.5 = 138.5 microM). This activity was NaN3, KCN and oligomycin insensitive but very sensitive to vanadate (I50 = 0.5 microM) suggesting its being neither mitochondrial or microsomal but plasma membrane in origin. Under optimal conditions of protein, hydrogen ion and substrate concentration, 16-19 nmoles phosphate was released per min per mg protein. Hill plot analysis indicated no cooperativity to occur between Ca2+ binding sites. Nucleotides other than ATP and dATP were ineffective as substrates. The trivalent cation, lanthanum (La3+) completely inhibited hydrolysis of ATP at approximately 70 microM (I50 = 25 microM). Calmodulin antagonists trifluoperazine and calmidazolium inhibited ATP hydrolysis in a dose dependent fashion.
SV40 转化的 WI38 肺成纤维细胞匀浆中 Ca2+ 刺激的、Mg2+ 依赖的 ATP 酶对 Ca2+ 具有高亲和力（K0.5 = 0.20 微摩尔），对 ATP（Km = 28.6 微摩尔）和 Mg2+（K0.5 = 138.5 微摩尔）具有中等程度的高亲和力。该活性对叠氮化钠、氰化钾和寡霉素不敏感，但对钒酸盐非常敏感（I50 = 0.5 微摩尔），这表明其起源既不是线粒体也不是微粒体，而是质膜。在蛋白质、氢离子和底物浓度的最佳条件下，每毫克蛋白质每分钟释放 16 - 19 纳摩尔磷酸盐。希尔图分析表明 Ca2+ 结合位点之间不存在协同作用。除 ATP 和 dATP 外的核苷酸作为底物无效。三价阳离子镧（La3+）在约 70 微摩尔（I50 = 25 微摩尔）时完全抑制 ATP 的水解。钙调蛋白拮抗剂三氟拉嗪和氯米帕明以剂量依赖方式抑制 ATP 水解。
