Influence of fructose 2,6-bisphosphate on the aggregation properties of rat liver phosphofructokinase

• Published in: The Journal of biological chemistry Vol. 258; no. 18; pp. 10827 - 10830
• Main Author: Reinhart, G D
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 25.09.1983; American Society for Biochemistry and Molecular Biology
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Enzymes and enzyme inhibitors; Fluorescence Polarization; Fructosediphosphates - pharmacology; Fundamental and applied biological sciences. Psychology; Hexosediphosphates - pharmacology; Liver - enzymology; Macromolecular Substances; Male; Phosphofructokinase-1 - metabolism; Rats; Transferases; Polarization; Vertebrata; Mammalia; Rat; Enzyme; Fluorescent labelling; Liver; Rodentia; Fluorescence; Molecular interaction; Molecular aggregation; 6-Phosphofructokinase
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(17)44348-1

The influence that fructose 2,6-bisphosphate (Fru-2,6-BP) has on the aggregation properties of rat liver phosphofructokinase has been studied by observing the fluorescence polarization of the enzyme covalently bound to the fluorescent probe pyrenebutyric acid. Fru-2,6-BP dramatically slows the dissociation of the high molecular weight aggregate forms of the enzyme when the enzyme is diluted to 3.2 micrograms/ml (4 X 10(-8) M subunits). Furthermore, Fru-2,6-BP is a strong promoter of reassociation to tetramer and larger forms if the enzyme has been previously allowed to dissociate to the dimer in its absence. Unlike many other positive effectors of liver phosphofructokinase, Fru-2,6-BP is also able to overcome the tendency of MgATP to promote tetramer formation and instead stabilize a very high degree of high molecular weight aggregate formation even in the presence of MgATP. The apparent affinity of liver phosphofructokinase for Fru-2,6-BP was measured by its ability to promote reassociation and compared to that for Fru-1,6-BP. The apparent dissociation constant for Fru-2,6-BP under these conditions is 36 microM, about 40-fold lower than the value of 1.4 mM measured for Fru-1,6-BP. Both ligands demonstrate synergism with the substrate Fru-6-P, which can lower the dissociation constant for Fru-2,6-BP 9-fold to 4 microM and that for Fru-1,6-BP 5-fold to 0.28 mM. These data are interpreted to suggest that influencing the aggregation state of rat liver phosphofructokinase may be one way in which Fru-2,6-BP achieves its effects on the enzyme in vivo.