We have examined the roles of Asp1018, Glu1027, Arg469 and Asp471 in the allosteric domain of
Rhizobium etli pyruvate carboxylase. Arg469 and Asp471 interact directly with the allosteric activator
acetyl coenzyme A (acetyl CoA) and the R469S and R469K mutants showed increased enzymic
activity in the presence and absence of acetyl CoA, whilst the D471A mutant exhibited no acetyl
CoA-activation. E1027A, E1027R and D1018A mutants had increased activity in the absence of acetyl
CoA, but not in its presence. These results suggest that most of these residues impose restrictions on
the structure and/or dynamics of the enzyme to affect activity.