Lester H A, Steer M L, Levitzki A
Proc Natl Acad Sci U S A. 1982 Feb;79(3):719-23. doi: 10.1073/pnas.79.3.719.
In membranes purified from human blood platelets, basal guanosine triphosphate (GTP) hydrolysis is reduced by a factor of approximately 6 by exposure to N-ethylmaleimide (10 mM). This decreased background enables the detection of an additional GTP hydrolysis in the presence of prostaglandin E1 (PGE1). The PGE1-stimulated GTPase has several properties correlated with PGE1-stimulated adenylate cyclase in this preparation. The two enzymes have similar dose-response relationships (half-maximal stimulation at 0.1 microM PGE1). Exposure to cholera toxin blocks the PGE1-stimulated GTPase and activates adenylate cyclase. Both enzymes are activated by submicromolar concentrations of GTP, although the Km for the GTPase is about 10 times greater than that for the adenylate cyclase. The data are discussed in relation to the hypothesis that hormone-stimulated adenylate cyclase (i) is activated as a regulatory component binds a molecular of GTP and (ii) is deactivated as this molecule is hydrolyzed.
在从人血血小板中纯化得到的膜中,通过暴露于N-乙基马来酰亚胺(10 mM),基础鸟苷三磷酸(GTP)水解降低了约6倍。这种背景的降低使得在前列腺素E1(PGE1)存在的情况下能够检测到额外的GTP水解。在该制剂中,PGE1刺激的GTP酶具有与PGE1刺激的腺苷酸环化酶相关的几个特性。这两种酶具有相似的剂量反应关系(在0.1 microM PGE1时达到最大刺激的一半)。暴露于霍乱毒素会阻断PGE1刺激的GTP酶并激活腺苷酸环化酶。两种酶都被亚微摩尔浓度的GTP激活,尽管GTP酶的Km约为腺苷酸环化酶的10倍。结合以下假设对这些数据进行了讨论:激素刺激的腺苷酸环化酶(i)在调节成分结合一分子GTP时被激活,(ii)在该分子被水解时失活。