The mechanism of rat liver fructose-1,6-bisphosphate inhibition by fructose-2,6-bisphosphate
Beliaeva, N.F.; Nikulin, I.R.; Korovkin, F.
Biokhimiia 54(9): 1514-1519
1989
ISSN/ISBN: 0320-9725 PMID: 2556186 Document Number: 327284
It was found that a decrease in the activating cation (Mg2+) concentration below [A]0.5 causes the disappearance of cooperativity of the fructose 1.6-bisphosphatase substrate binding sites induced by high fructose 2.6-bisphosphate concentrations without any significant alteration in the extent of the enzyme inhibition. Under these conditions, a competitive type of inhibition (with respect to the substrate) is transformed into a non-competitive type with an increase in the fructose 2.6-bisphosphate concentration. The data obtained confirm the viewpoint that fructose 2.6-bisphosphate binds to the enzyme at two distinct sites, a catalytic and an allosteric ones, differing in their affinity for the inhibitor. It is supposed that the interaction between the allosteric fructose 2.6-bisphosphate binding site and the activator site occupied by Mg2+ is necessary for the cooperative response of the enzyme to the substrate.