Truncated forms of the recombinant Escherichia coli ADP-glucose pyrophosphorylase: The importance of the N-terminal region for allosteric activation and inhibition

Truncated forms of Escherichia coli ADPglucose pyrophosphorylase were const ructed using recombinant DNA techniques. A truncated form of the enzyme hav ing the first 11 amino acid residues from the N-terminus and 2 amino acid r esidues from the C-terminus deleted was found to be highly active in absenc e of activator. A 1.6-fold activation by 1.5 mM fructose 1,6 bis-phosphate was observed for the truncated enzyme as compared to the 30-fold activation seen for the intact enzyme. Inhibition of the truncated enzyme by AMP was less than that seen with the intact enzyme. Similar properties were display ed by an enzyme truncated only at the N-terminal. Conversely, the C-termina l truncated enzyme shortened by 2 amino acid residues at the C-terminus is as sensitive as the intact enzyme to activation and inhibition. These resul ts suggest that the N-terminal region is required for allosteric regulation of the enzyme. (C) 2001 Academic Press.