Gietzen K, Adamczyk-Engelmann P, Wüthrich A, Konstantinova A, Bader H
Biochim Biophys Acta. 1983 Dec 7;736(1):109-18. doi: 10.1016/0005-2736(83)90175-x.
Compound 48/80, a condensation product of N-methyl-p-methoxyphenethylamine with formaldehyde, is composed of a family of cationic amphiphiles differing in the degree of polymerization. Compound 48/80 was found to be a potent inhibitor of the calmodulin-activated fraction of brain phosphodiesterase and red blood cell Ca2+-transport ATPase, with IC50 values of 0.3 and 0.85 micrograms/ml, respectively. However, the basal activity of both enzymes is not at all suppressed by the drug at concentrations up to 300 micrograms/ml. Inhibition of Ca2+ transport into inside-out red blood cell vesicles by compound 48/80 follows a similar pattern in that basal, calmodulin-independent, transport is also not affected by the drug. Kinetic analysis revealed that the stimulation of Ca2+-transport ATPase induced by calmodulin is inhibited by compound 48/80 according to a competitive mechanism. It was demonstrated that the inhibitory constituents of compound 48/80 bind to calmodulin in a Ca2+-dependent fashion. Comparison of the specificity of several anti-calmodulin drugs showed that compound 48/80 is the most specific inhibitor of the calmodulin-dependent fraction of red blood cell Ca2+-transport ATPase that has been described hitherto. In addition, compound 48/80 was found to be a rather specific inhibitor of the calmodulin-induced activation of Ca2+-transport ATPase when compared with the stimulation induced by an anionic amphiphile or by limited proteolysis. Half-maximal inhibition of the activity stimulated by oleic acid or mild tryptic digestion required 8- and 32-times higher concentrations of compound 48/80, respectively, compared with the calmodulin-dependent fraction of the ATPase activity. Moreover, calmodulin-independent systems as rabbit skeletal muscle sarcoplasmic reticulum Ca2+-transport ATPase or calf cardiac sarcolemma (Na+ + K+)-transport ATPase are far less influenced by compound 48/80 as compared with trifluoperazine and calmidazolium. Because of its high specificity compound 48/80 is proposed to be a promising tool for studying calmodulin-dependent processes.
化合物48/80是N-甲基-对甲氧基苯乙胺与甲醛的缩合产物，由一系列聚合度不同的阳离子两亲物组成。已发现化合物48/80是脑磷酸二酯酶钙调蛋白激活部分和红细胞Ca2+转运ATP酶的有效抑制剂，IC50值分别为0.3和0.85微克/毫升。然而，在浓度高达300微克/毫升时，该药物对这两种酶的基础活性完全没有抑制作用。化合物48/80对红细胞内翻囊泡中Ca2+转运的抑制作用遵循类似模式，即基础的、不依赖钙调蛋白的转运也不受该药物影响。动力学分析表明，化合物48/80根据竞争机制抑制钙调蛋白诱导的Ca2+转运ATP酶的刺激作用。已证明化合物48/80的抑制成分以Ca2+依赖的方式与钙调蛋白结合。几种抗钙调蛋白药物特异性的比较表明，化合物48/80是迄今所描述的红细胞Ca2+转运ATP酶钙调蛋白依赖部分最特异的抑制剂。此外，与阴离子两亲物或有限蛋白酶解诱导的刺激相比，化合物48/80被发现是钙调蛋白诱导的Ca2+转运ATP酶激活的相当特异的抑制剂。与ATP酶活性的钙调蛋白依赖部分相比，油酸或轻度胰蛋白酶消化刺激的活性的半数最大抑制分别需要高8倍和32倍浓度的化合物48/80。此外，与三氟拉嗪和氯米达唑相比，不依赖钙调蛋白的系统如兔骨骼肌肌浆网Ca2+转运ATP酶或小牛心肌肌膜（Na+ + K+）转运ATP酶受化合物48/80的影响要小得多。由于其高特异性，化合物48/80被认为是研究钙调蛋白依赖过程的一种有前途的工具。
