Bacterial ADP-glucose pyrophosphorylases are allosterically regulated by metabolites that are key intermediates of central pathways in the respective microorganism. Pyruvate (Pyr) and fructose 6-phosphate (Fru6P) activate the enzyme from Agrobacterium tumefaciens by increasing Vmax about 10- and 20-fold, respectively. Here, we studied the combined effect of both metabolites on the enzyme activation. Our results support a model in which there is a synergistic binding of these two activators to two distinct sites and that each activator leads the enzyme to distinct active forms with different properties. In presence of both activators, Pyr had a catalytically dominant effect over Fru6P determining the active conformational state. By mutagenesis we obtained enzyme variants still sensitive to Pyr activation, but in which the allosteric signal by Fru6P was disrupted. This indicated that the activation mechanism for each effector was not the same. The ability for this enzyme to have more than one allosteric activator site, active forms, and allosteric signaling mechanisms is critical to expand the evolvability of its regulation. These synergistic interactions between allosteric activators may represent a feature in other allosteric enzymes.

中文翻译：

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丙酮酸和果糖6-磷酸同时激活根癌农杆菌ADP-葡萄糖焦磷酸化酶。

细菌ADP-葡萄糖焦磷酸化酶被代谢物变构调节，代谢物是各个微生物中枢途径的关键中间体。丙酮酸（Pyr）和果糖6-磷酸（Fru6P）通过分别将Vmax增加约10倍和20倍来激活根癌土壤杆菌的酶。在这里，我们研究了两种代谢物对酶激活的综合作用。我们的结果支持一种模型，其中两个激活剂协同结合到两个不同的位点，并且每个激活剂都将酶引导至具有不同特性的不同活性形式。在两种激活剂的存在下，Pyr都比Fru6P具有催化显性作用，从而确定了活性构象状态。通过诱变，我们获得了对Pyr激活仍然敏感的酶变体，但其中Fru6P的变构信号被破坏了。这表明每个效应子的激活机制是不同的。该酶具有不止一个变构激活位点，活性形式和变构信号传导机制的能力对于扩大其调控的可进化性至关重要。变构活化剂之间的这些协同相互作用可能代表其他变构酶的特征。