Wiemer G, Kaiser G, Palm D
Naunyn Schmiedebergs Arch Pharmacol. 1978 Jun;303(2):145-52. doi: 10.1007/BF00508060.
In membrane preparations from immature erythrocytes from rats the effects of the divalent cations Mg2+, Mn2+ and Ca2+ on basal activity of adenylcyclase as well as on enzyme activity stimulated by isoprenaline (Ipn) or guanylyl-imidodiphosphate [Gpp(NH)p] were investigated.--Mn2+ is a ten-fold stronger activator of the enzyme than Mg2+ irrespective of the stimulant used. At suboptimal concentrations of the cations at all concentrations of Gpp(NH)p used (10(-6) to 10(-3) M) reaction velocities increase progressively over an incubation period of 40 min. Optimal cation concentrations, however, i.e. 3 x 10(-3) M Mn2+ and 3 x 10(-2)M Mg2+ elicit a constant and at 10(-4) M Gpp(NH)p maximal reaction velocity. In contrast, the Ipn-stimulated cAMP synthesis proceeds linearly at all Ipn concentrations used; a change of cation concentrations elicits only a change in reaction velocity, which is maximal at 10(-3) M Mn2+ and 10(-2) M Mg2+ respectively.--Ca2+ inhibits adenylcyclase activity in a non-competitive manner, irrespective of the stimulant and ion concentration used. The Mg2+-activated enzyme, however, is more susceptible to the inhibiting effect of Ca2+ than the Mn2+-activated enzyme.--It is concluded that Mn2+ and Mg2+ are allosteric effectors of the enzyme adenylcyclase, acting at a Me2+-site of the catalytic unit of adenylcyclase.
在大鼠未成熟红细胞的膜制剂中，研究了二价阳离子Mg2+、Mn2+和Ca2+对腺苷酸环化酶基础活性以及对异丙肾上腺素（Ipn）或鸟苷酰亚胺二磷酸[Gpp(NH)p]刺激的酶活性的影响。——无论使用何种刺激剂，Mn2+作为该酶的激活剂，其活性比Mg2+强十倍。在所有使用的Gpp(NH)p浓度（10(-6)至10(-3)M）下，当阳离子浓度处于次优浓度时，在40分钟的孵育期内反应速度会逐渐增加。然而，最佳阳离子浓度，即3×10(-3)M Mn2+和3×10(-2)M Mg2+，在10(-4)M Gpp(NH)p时会引发恒定且最大的反应速度。相比之下，在所有使用的Ipn浓度下，Ipn刺激的cAMP合成呈线性进行；阳离子浓度的变化仅引起反应速度的变化，分别在10(-3)M Mn2+和10(-2)M Mg2+时达到最大。——无论使用何种刺激剂和离子浓度，Ca2+均以非竞争性方式抑制腺苷酸环化酶活性。然而，Mg2+激活的酶比Mn2+激活的酶对Ca2+的抑制作用更敏感。——得出的结论是，Mn2+和Mg2+是腺苷酸环化酶的变构效应剂，作用于腺苷酸环化酶催化单元的Me2+位点。
