钙和钙调蛋白对兔肠上皮细胞腺苷酸环化酶的调节作用。

Regulation by calcium and calmodulin of adenylate cyclase from rabbit intestinal epithelium.

作者信息

Lazo P S, Rivaya A, Velasco G

出版信息

Biochim Biophys Acta. 1984 Apr 24;798(3):361-7. doi: 10.1016/0304-4165(84)90110-7.

Abstract

The effect of calcium on adenylate cyclase from rabbit small intestine has been studied using a particulate preparation obtained from isolated epithelial cells. Both basal and vasoactive intestinal peptide-stimulated activities were inhibited by calcium concentrations in the micromolar range. In the presence of calmodulin, a biphasic response was obtained. At low calcium concentration (4 X 10(-9)-6 X 10(-8) M) the enzyme was activated up to 50%. As the Ca2+ concentration was increased, the enzyme was concomitantly inhibited. Half-maximal inhibition of calmodulin-dependent activity was obtained at 1 microM free Ca2+. The activation of the enzyme was also dependent on the concentration of Mg2+. At less than 1 microM Ca2+, the enzyme exhibited a biphasic response, being activated at below 3 mM Mg2+ and inhibited at higher concentrations. At Ca2+ concentrations that were inhibitory, the enzyme did not show the biphasic response to Mg2+. At concentrations above 3 mM, the maximal rate (Vmax) remained constant. Vmax was inversely proportional to the concentration of Ca2+ present. Calmodulin altered Vmax when acting on vasoactive intestinal peptide-stimulated enzyme. Calmodulin had no effect on the Km for hormone activation. The calmodulin-dependent activity was inhibited by incubation with trifluoperazine.

摘要

利用从分离的上皮细胞获得的微粒体制剂，研究了钙对兔小肠腺苷酸环化酶的影响。基础活性和血管活性肠肽刺激的活性均受到微摩尔浓度钙的抑制。在存在钙调蛋白的情况下，获得了双相反应。在低钙浓度（4×10⁻⁹ - 6×10⁻⁸ M）时，酶被激活高达50%。随着Ca²⁺浓度增加，酶随之被抑制。在1 microM游离Ca²⁺时获得钙调蛋白依赖性活性的半数最大抑制。酶的激活也依赖于Mg²⁺的浓度。在低于1 microM Ca²⁺时，酶表现出双相反应，在低于3 mM Mg²⁺时被激活，在较高浓度时被抑制。在Ca²⁺浓度具有抑制作用时，酶对Mg²⁺不显示双相反应。在高于3 mM的浓度下，最大反应速率（Vmax）保持恒定。Vmax与存在的Ca²⁺浓度成反比。钙调蛋白作用于血管活性肠肽刺激的酶时会改变Vmax。钙调蛋白对激素激活的Km没有影响。钙调蛋白依赖性活性通过与三氟拉嗪孵育而被抑制。