Horio Y, Murad F
Department of Pharmacology, Northwestern University Medical School, Chicago, Illinois 60611.
J Biol Chem. 1991 Feb 25;266(6):3411-5.
Guanylyl cyclase from bovine rod outer segments was solubilized using Triton X-100 and a high concentration of KCl, and its regulation was studied. The efficiency of solubilization was about 50-90% of total activity. When the Ca2+ content was lowered (less than 80 nM), guanylyl cyclase was activated about 2-fold. In the presence of higher concentrations of Ca2+ (greater than 140 nM), the activity was decreased. The regulation by Ca2+ was also demonstrated with solubilized preparations. In the presence of 186 nM Ca2+ which inhibited guanylyl cyclase, La3+ activated the enzyme about 2-fold, suggesting that the Ca2(+)-binding protein similar to other Ca2(+)-binding proteins associates with guanylyl cyclase regulation. Sodium nitroprusside and nitric oxide which are activators of soluble guanylyl cyclase in other tissues also activated the retinal guanylyl cyclase. Maximum activation by sodium nitroprusside was 20-fold using Mg2+ as a cofactor. Activation by nitric oxide and related compounds suggests that retinal guanylyl cyclase contains a heme prosthetic group that may participate in a novel regulatory mechanism for this enzyme.
使用 Triton X - 100 和高浓度的 KCl 溶解来自牛视杆细胞外段的鸟苷酸环化酶，并对其调节作用进行了研究。溶解效率约为总活性的 50 - 90%。当 Ca2+ 含量降低（低于 80 nM）时，鸟苷酸环化酶的活性被激活约 2 倍。在较高浓度的 Ca2+（大于 140 nM）存在时，活性降低。Ca2+ 的调节作用在溶解制剂中也得到了证实。在 186 nM Ca2+ 抑制鸟苷酸环化酶的情况下，La3+ 使该酶的活性激活约 2 倍，这表明类似于其他 Ca2+ 结合蛋白的 Ca2(+) 结合蛋白与鸟苷酸环化酶的调节相关。硝普钠和一氧化氮作为其他组织中可溶性鸟苷酸环化酶的激活剂，也能激活视网膜鸟苷酸环化酶。以 Mg2+ 作为辅因子时，硝普钠的最大激活倍数为 20 倍。一氧化氮及相关化合物的激活作用表明，视网膜鸟苷酸环化酶含有一个血红素辅基，可能参与该酶的一种新型调节机制。
