Lacombe M L, Hanoune J
J Biol Chem. 1979 May 25;254(10):3697-9.
Guanylate cyclase activity (GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2.), measured in purified rat liver plasma membranes, was markedly increased by treatment with various purified proteases. The effect was maximal with trypsin, alpha-chymotrypsin, papain, and thermolysin (6- to 8-fold increase with 5 to 20 microgram of protease/ml) and lower with subtilisin and elastase (3- to 4-fold increase). The activation was due to an increase in the maximal velocity of the cyclizing reaction. No modification was observed either in the apparent affinity for the substrate MnGTP or in the cooperative behavior of the enzyme kinetics which displayed Hill coefficients of 1.6 for both basal and activated states. The Triton X-100-dispersed guanylate cyclase remained sensitive to papain, which suggests that the action of proteases was not restricted to an indirect action upon the membranous environment of the guanylate cyclase. In contrast, the cytosolic soluble guanylate cyclase, assayed in the presence or absence of sodium azide, was absolutely insensitive to papain. Thus, proteolysis represents a previously undescribed mechanism for activating membranous guanylate cyclase systems, which might be of importance in the physiological regulation of this enzyme.
在纯化的大鼠肝细胞膜中测量的鸟苷酸环化酶活性（GTP 焦磷酸裂解酶（环化），EC 4.6.1.2.），通过用各种纯化的蛋白酶处理而显著增加。用胰蛋白酶、α-胰凝乳蛋白酶、木瓜蛋白酶和嗜热菌蛋白酶处理时效果最佳（每毫升 5 至 20 微克蛋白酶可使活性增加 6 至 8 倍），而枯草杆菌蛋白酶和弹性蛋白酶的效果较低（增加 3 至 4 倍）。这种激活是由于环化反应的最大速度增加。在对底物 MnGTP 的表观亲和力或酶动力学的协同行为方面均未观察到改变，其在基础状态和激活状态下的希尔系数均为 1.6。Triton X-100 分散的鸟苷酸环化酶对木瓜蛋白酶仍敏感，这表明蛋白酶的作用不限于对鸟苷酸环化酶膜环境的间接作用。相反，在有无叠氮化钠存在的情况下测定的胞质可溶性鸟苷酸环化酶对木瓜蛋白酶绝对不敏感。因此，蛋白水解代表了一种以前未描述的激活膜鸟苷酸环化酶系统的机制，这可能在该酶的生理调节中具有重要意义。
