Regulation of Dictyostelium discoideum adenylate cyclase by manganese and adenosine analogs.
Regulation of Dictyostelium discoideum adenylate cyclase by manganese and adenosine analogs.
复制标题
锰和腺苷类似物对盘基网柄菌腺苷酸环化酶的调节。
DOI：
10.1016/0167-4889(87)90140-6
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发表时间：
1987
期刊：
影响因子：
--
通讯作者：
Howlett,A
中科院分区：
文献类型：
--
作者：
Khachatrian,L;Klein,C;Howlett,A
腺苷酸环化酶是盘基网柄阿米巴趋化信号传递机制中的关键酶。然而，由于粗裂解物中酶活性的不稳定性，很少有研究检查这种酶的调节在体外进行。对于本通讯中介绍的研究，已分离出一种膜制剂，其显示出高比活性腺苷酸环化酶，在−70°C储存期间和27°C测定条件下稳定。该酶被微摩尔浓度的MnCl 2激活。GTP和它的非水解类似物鸟苷5′-（β，γ-亚氨基）三磷酸在Mg ~（2+）或Mn ~（2+）存在下非竞争性地抑制该酶。然而，在Mn 2+存在的情况下，这种抑制作用更加明显。由于鸟苷酸环化酶在D.盘状膜的腺苷酸环化酶活性低于10%，鸟苷酸环化酶对环AMP的产生没有显著的贡献。实验表明，D.腺苷酸环化酶也受腺苷类似物的调节。2′，5 ′-二脱氧腺苷和2′-脱氧腺苷对该酶有抑制作用，Mn ~（2+）的存在增强了该酶的抑制作用。然而，抑制是不完全一致的，这将是真核系统的P-位点的预期，因为一些嘌呤修饰的腺苷类似物也抑制酶。鸟嘌呤核苷酸对嘌呤修饰或核糖修饰的腺苷类似物的抑制作用没有影响。环腺苷酸与D.盘状突膜不受MnCl 2或腺苷类似物的影响。
Adenylate cyclase is the critical enzyme in the chemotactic signal relay mechanism of the slime mold amoeba,Dictyostelium discoideum. However, few studies examining the regulation of this enzyme have been performed in vitro due to the instability of enzyme activity in crude lysates. For studies presented in this communication, a membrane preparation has been isolated that exhibits a high specific activity adenylate cyclase that is stable during storage at −70°C and under assay conditions at 27°C. The enzyme was activated by micromolar concentrations of MnCl2. GTP and its non-hydrolyzable analog, guanosine 5′-(β,γ-imino)triphosphate, inhibited the enzyme non-competitively in the presence of either Mg2+or Mn2+. However, this inhibition was more pronounced in the presence of Mn2+. Since guanylate cyclase activity in theD. discoideummembranes was less than 10% of the adenylate cyclase activity, there could not be a significant contribution by guanylate cyclase toward the production of cyclic AMP. Experiments indicate thatD. discoideumadenylate cyclase was also regulated by adenosine analogs. The enzyme was inhibited by 2′,5′-dideoxyadenosine and 2′-deoxyadenosine and inhibition was augmented by the presence of Mn2+. However, the inhibition was not entirely consistent with that which would be expected for the P-site of eukaryotic systems because some purine-modified adenosine analogs also inhibited the enzyme. Guanine nucleotides had no effect on the inhibition by either purine-modified or ribose-modified adenosine analogs. The binding of cyclic AMP to its receptor on theD. discoideummembranes was not affected by either MnCl2or adenosine analogs.