Haldane relationships calculation

In order to calculate the Haldane relationship for the Ordered Bi Bi mechanism, the concentration of one pair of reactants must be set to zero (Cleland, 1982). If the concentrations of A and B is negligible, it is expected that the general rate Eq. (4.39) reduces to the rate equation for the reverse reaction in the presence of P and Q, and absence of A and B ... 

Note, however, that the product inhibition studies in the A P -1- Q direction do not allow Jfp and Kq to be determined, but their ratio can be calculated from the Haldane relationship (Eq. (9.45)) ... 

Kinetic constants in Table 5 may be applied directly to calculate the thermodynamic equilibrium constant Keq and compare with the same constant obtained by independent methods. Testing for consistency with Haldane relationships is theoretically a good method, but in practice involves the combination of large numbers of constants, each of which may be in error to some degree the real use of Haldanes is to ensure that the experimental data are self-consistent. 

Relationship (10.66) is typical for reactions catalyzed by NAD(P)-dependent dehydrogenases, such as the oxidation of alcohols catalyzed by the yeast (Leskovac et cd., 1996) or the horse liver alcohol dehydrogenase (Plapp et al, 1986), and serves to calculate the and to check the internal consistency of Haldane relationships. 

Experimental verification of this relationship was found when iiC was calculated from F .x and Km values at different pH values. In experiments carried out in various concentrations of phosphate and at varying pH values, the ratio Fm.x fumarate/Fm x malate varied by a factor of 65, but the Aeq calculated by using the Haldane equation was found to be remarkably constant, averaging 4.4 at 25°C. 

---