Inhibition by substrate of fructose 1,6-bisphosphatase purified from rat kidney cortex. Calculation of the kinetic constants of the enzyme.

Fructose 1,6-bisphosphatase is a typical enzyme that is severely inhibited by its own substrate. This makes it difficult to determine all the parameters involved in its kinetics. It has been shown recently that if Vm is satisfactorily estimated the remaining parameters can be determined using the Hill plot (Bounias, M. (1988) Biochem. Int. 17, 147-154). The enzyme has been purified from rat kidney cortex nearly to homogeneity, and its kinetic constants have been calculated using a rigorous algebraic method. The most interesting result is that the substrate is unable to bind to the free enzyme as an inhibitor, which indicates that the enzyme lacks an allosteric site for hexose bisphosphates.