PMID:3161887
| Citation |
Guixé, V and Babul, J (1985) Effect of ATP on phosphofructokinase-2 from Escherichia coli. A mutant enzyme altered in the allosteric site for MgATP. J. Biol. Chem. 260:11001-5 |
|---|---|
| Abstract |
The activity of Escherichia coli phosphofructokinase-2 (Pfk-2) and of the mutant enzyme Pfk-2* was measured over a wide range of Mg2+ and ATP concentrations. MgATP2- inhibited only the Pfk-2 enzyme, with a degree of cooperativity of 1.5. This inhibition was relieved upon increasing the fructose-6-P concentration or by lowering the pH of the reaction mixture. Other nucleotides used as phosphate donors instead of ATP did not inhibit. MgATP2- was the true substrate for both enzymes and their Km values for this compound were not affected by an increase of the free Mg2+ concentration. However, free Mg2+ partially relieved the MgATP2- inhibition of Pfk-2 under conditions where the ATP4- concentration was negligible, without changes in the degree of cooperativity. ATP4- acted as a strong competitive inhibitor of both Pfk-2 and Pfk-2* with respect to MgATP2- with Ki values of 10 and 8 microM, respectively. ADP, AMP, and cAMP did not prevent the MgATP2- inhibition of Pfk-2. These results suggest the presence of an allosteric site for MgATP2- in Pfk-2 responsible for the MgATP2- inhibition, which is altered in Pfk-2* as a consequence of the structural mutation. |
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| Keywords |
Adenosine Triphosphate/metabolism; Adenosine Triphosphate/pharmacology; Allosteric Site; Escherichia coli/enzymology; Kinetics; Magnesium/pharmacology; Mutation; Phosphofructokinase-1/genetics; Phosphofructokinase-1/metabolism; Ribonucleotides/metabolism; Substrate Specificity |
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