Davis B, Lazarus N R
Biochem J. 1972 Sep;129(2):373-9. doi: 10.1042/bj1290373.
The adenylate cyclase system of normal mouse islets was characterized. The pH optimum of the system was 7.6. The enzyme preparation contained particulate phosphodiesterase activity. This could be removed by treatment with 0.4% (v/v) Triton X-100 or inhibited by 8mm-theophylline in the presence of 2mm-cyclic AMP (adenosine 3':5'-cyclic monophosphate). ATP at 0.32mm produced one-half maximal enzyme activity. The enzyme was stimulated in the presence of F(-) and strongly inhibited by Ca(2+). The isolated enzyme retained hormonal sensitivity and was stimulated by glucagon, pancreozymin and secretin at physiological concentrations. Glucose at 17mm, 8mm and 2mm had no direct effect on the activity of the enzyme; neither did galactose at the same concentrations. Groups of islets incubated in 17mm- or 2mm-glucose for 5 or 15min and then homogenized and assayed for adenylate cyclase activity showed no differences in adenylate cyclase activity. The results suggest that the mechanism of glucose-mediated insulin release is not via the adenylate cyclase system. Hormones, however, could mediate insulin secretion via their effects on the adenylate cyclase system.
对正常小鼠胰岛的腺苷酸环化酶系统进行了特性研究。该系统的最适pH值为7.6。酶制剂含有颗粒状磷酸二酯酶活性。这可以通过用0.4%（v/v） Triton X - 100处理去除，或者在存在2mM环磷酸腺苷（腺苷3':5'-环一磷酸）的情况下被8mM茶碱抑制。0.32mM的ATP产生最大酶活性的一半。该酶在F(-)存在时受到刺激，而被Ca(2+)强烈抑制。分离出的酶保留了激素敏感性，并在生理浓度下受到胰高血糖素、促胰液素和促胰酶素的刺激。17mM、8mM和2mM的葡萄糖对该酶的活性没有直接影响；相同浓度的半乳糖也没有影响。将胰岛分组在17mM或2mM葡萄糖中孵育5或15分钟，然后匀浆并测定腺苷酸环化酶活性，结果显示腺苷酸环化酶活性没有差异。结果表明，葡萄糖介导的胰岛素释放机制不是通过腺苷酸环化酶系统。然而，激素可以通过其对腺苷酸环化酶系统的作用来介导胰岛素分泌。
