Aurbach G D, Spiegel A M, Gardner J D
Adv Cyclic Nucleotide Res. 1975;5:117-32.
(1) Interaction of beta-adrenergic catecholamines with specific receptors on the cell membrane causes activation of adenylate cyclase, generation of intracellular cyclic 3',5'-AMP, and enhanced sodium and potassium transport. The effects of catecholamines on each of these functions are characteristic of beta1-type receptor interactions and are specific for 1(--)isomers. The order of effectiveness of agonists is isoproterenol greater than norepinephrine approximately equal to epinephrine. (2) exogenous cyclic 3',5'-AMP enhances sodium or potassium transport in a fashion identical to that caused by catecholamines. (3) the receptor contains an ethanolamine site that recognizes the stereospecific function of the agonist. Interaction at this site can be determined by measuring specific binding of a high specific activity-radioiodinated beta-blocker analogue (125-iodohydroxybenzylpindolol). Catecholamines bind at this site with affinities that parallel their biologic effectiveness as beta-adrenergic agonist. Beta-Blockers interact at this site with affinities that parallel their potencies as specific inhibitors of biologic function. (4) the adenylate cyclase complex contains a receptor site for guanyl nucleotides that is distinct from the catalytic site for ATP. Interaction at this site can be determined by measuring binding of radioactive guanylylimidodiphosphate (GMPPNP). GMPPNP markedly enhances the adenylate cyclase response to beta-adrenergic catecholamines with a 10-fold increase in apparent affinity of isoproterenol for activation of adenylate cyclase. Concomitantly there is a shift in Km and Vmax for ATP at the catalytic site. (5) Activation of adenylate cyclase by agonist or GMPPNP alone is reversible (GMPPNP remains bound even though the system returns to basal activity). The addition of isoproterenol plus GMPPNP, however, results in a state of enzyme activity which is apparently irreversible even though, under these conditions, the beta-adrenergic catecholamine freely dissociates from its receptor site. Under these conditions also the activated enzyme is not inhibited by the specific beta-blocker propranolol. (6) There is no evidence under adenylate cyclase assay conditions for a direct interaction of guanyl nucleotides with the beta-adrenergic receptor site nor for direct interaction of the agonist with the guanyl nucleotide site.
（1）β-肾上腺素能儿茶酚胺与细胞膜上的特定受体相互作用，导致腺苷酸环化酶激活、细胞内3',5'-环磷酸腺苷生成以及钠和钾转运增强。儿茶酚胺对这些功能中每一项的作用都是β1型受体相互作用的特征，且对1（-）异构体具有特异性。激动剂的效力顺序为异丙肾上腺素大于去甲肾上腺素，约等于肾上腺素。（2）外源性3',5'-环磷酸腺苷以与儿茶酚胺引起的方式相同的方式增强钠或钾转运。（3）该受体含有一个乙醇胺位点，可识别激动剂的立体特异性功能。该位点的相互作用可通过测量高比活放射性碘标记的β-阻滞剂类似物（125-碘羟基苄基吲哚洛尔）的特异性结合来确定。儿茶酚胺以与其作为β-肾上腺素能激动剂的生物学效力平行的亲和力结合于此位点。β-阻滞剂以与其作为生物学功能特异性抑制剂的效力平行的亲和力在此位点相互作用。（4）腺苷酸环化酶复合物含有一个鸟苷酸核苷酸受体位点，该位点与ATP催化位点不同。该位点的相互作用可通过测量放射性鸟苷酰亚胺二磷酸（GMPPNP）的结合来确定。GMPPNP显著增强腺苷酸环化酶对β-肾上腺素能儿茶酚胺的反应，异丙肾上腺素激活腺苷酸环化酶的表观亲和力增加10倍。同时，催化位点处ATP的Km和Vmax发生偏移。（5）单独由激动剂或GMPPNP激活腺苷酸环化酶是可逆的（即使系统恢复到基础活性，GMPPNP仍保持结合状态）。然而，加入异丙肾上腺素加GMPPNP会导致酶活性状态明显不可逆，即使在这些条件下，β-肾上腺素能儿茶酚胺可从其受体位点自由解离。在这些条件下，活化的酶也不会被特异性β-阻滞剂普萘洛尔抑制。（6）在腺苷酸环化酶测定条件下，没有证据表明鸟苷酸核苷酸与β-肾上腺素能受体位点直接相互作用，也没有证据表明激动剂与鸟苷酸核苷酸位点直接相互作用。
