Interaction between the carboxyl groups of Asp127 and Asp129 in the active site of Escherichia coli phosphofructokinase

摘要: The pH dependence of the enzymic properties phosphofructokinase from Escherichia coli was compared to those two mutants in which one carboxyl group active site has been removed either Asp127 or Asp129. All measurements activity were made presence allosteric activator ADP GDP eliminate any cooperative process. Asp129 is a crucial residue for since its conversion Ser decreases catalytic by 2-3 orders magnitude both forward and reverse reactions, but ionization not directly related activity. This however modified Asp129----Ser mutation, pK another residue, Asp127, as much 1.5. side chain role proposed earlier: deprotonated form acts base reaction, protonated an acid reaction. also required binding fructose 1,6-bisphosphate. electrostatic interaction between groups seems different free that enzyme/substrate complexes, suggesting conformational change occurs upon substrate binding. involves other ionizable with approximately 6 does belong chains