Kotlarz D, Buc H
Eur J Biochem. 1981 Jul;117(3):569-74. doi: 10.1111/j.1432-1033.1981.tb06375.x.
Escherichia coli K12 contains two phosphofructokinases: phosphofructokinase 1, the most studied one, appears to behave as an allosteric enzyme, while phosphofructokinase 2 presents the features of a Michaelian enzyme. We show the present paper that, in fact, phosphofructokinase 2 also presents some regulatory properties in vitro: at high concentrations, ATP is an inhibitor of phosphofructokinase 2 and it provokes the tetramerization of the dimeric native enzyme. The binding of the two substrates to phosphofructokinase 2 is sequential and ordered as for phosphofructokinase 1, but in the former case fructose 6-phosphate is the first substrate to be bound and ADP the first product to be released. Each dimer of phosphofructokinase 2 binds two molecules of fructose 6-phosphate but only one molecule of the product fructose 1,6-phosphate. Although both phosphofructokinases of E. coli K12 present regulatory properties in vitro, the mechanism of regulation of the activity of the two enzymes is strikingly different. It can be asked whether or not these mechanisms operate in vivo.
大肠杆菌K12含有两种磷酸果糖激酶：研究最多的磷酸果糖激酶1似乎表现为别构酶，而磷酸果糖激酶2则呈现米氏酶的特征。我们在本文中表明，实际上，磷酸果糖激酶2在体外也呈现出一些调节特性：在高浓度时，ATP是磷酸果糖激酶2的抑制剂，并且它会促使二聚体天然酶发生四聚化。与磷酸果糖激酶1一样，两种底物与磷酸果糖激酶2的结合是顺序有序的，但在前一种情况下，6-磷酸果糖是首先结合的底物，ADP是首先释放的产物。磷酸果糖激酶2的每个二聚体结合两分子的6-磷酸果糖，但仅结合一分子的产物1,6-二磷酸果糖。尽管大肠杆菌K12的两种磷酸果糖激酶在体外都具有调节特性，但两种酶活性的调节机制却截然不同。可以提出这些机制在体内是否起作用的问题。
