Temperature-induced inversion of allosteric phenomena

• Published in: The Journal of biological chemistry Vol. 269; no. 1; pp. 47 - 50
• Main Authors: Braxton, B.L., Tlapak-Simmons, V.L., Reinhart, G.D.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 07.01.1994
• Subjects: Allosteric Regulation; Analytical, structural and metabolic biochemistry; Bacillus stearothermophilus; Biological and medical sciences; Carbamoyl-Phosphate Synthase (Glutamine-Hydrolyzing) - metabolism; Enzymes and enzyme inhibitors; Escherichia coli; Escherichia coli - enzymology; Fundamental and applied biological sciences. Psychology; General aspects, investigation methods; Geobacillus stearothermophilus - enzymology; Phosphofructokinase-1 - metabolism; Temperature; Thermodynamics; Ligand binding; Temperature; Carbon-nitrogen ligases; Enzyme; Carbamoyl-phosphate synthase (glutamine-hydrolysing); Transferases; Escherichia coli; Allostery; Bacillaceae; Regulation(control); Bacillales; Ligases; Bacillus stearothermophilus; Bacteria; Enterobacteriaceae; 6-Phosphofructokinase
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/s0021-9258(17)42309-x

Two instances, involving the enzymes carbamoyl-phosphate synthetase from Escherichia coli and phosphofructokinase from Bacillus stearothermophilus, respectively, are described in which increasing temperature alone causes the actions of an allosteric ligand to change from inhibition to activation. In neither case are these effects due to a change in the activation energy of the enzyme catalyzed reaction induced by the allosteric ligand. Rather, they are due to temperature-dependent changes in the extent to which the binding of allosteric ligand modifies the affinity of the enzyme for substrate. The data can be readily explained by an analysis of the apparent delta H and delta S components of the coupling free energy, which quantitatively describe the actions of allosteric ligands that act in this manner. These observations underscore the shortcomings of expecting to explain the actions of an allosteric ligand solely by the structural perturbations that accompany the binding of an allosteric ligand such as those often revealed by x-ray crystallography.