Example enzyme kinetics of citrate synthase

Note that only states that are expected to be significant in the pH and ionic range studied are included in these calculations. Therefore some binding polynomials do not include terms for all possible cation-bound states. Given these forms of the binding polynomials, the relationships between the reference species concentrations and the reactant concentrations take the usual form  

The apparent equilibrium constant for the biochemical reaction is computed as a function of pH, [K+], and [Mg2+]  

In this mechanism only the third reaction (in which hydrogen ion explicitly appears) depends on pH. Since Kep, the equilibrium constant for the third reaction, depends on pH while the others do not, we compute Kep as a function of the equilibrium constant for the reference reaction 

The rate constant k-3 is assumed to depend on pH according to the formula k- = (h/10—7)2 43 where k 43 is independent of pH. Therefore the kinetic constant Kmp is defined to depend on pH as 

Kinetic parameter values for citrate synthase for several isoforms of the model may be estimated for the general analysis of the compulsory-order ternary mechanism outlined in Section 4.4.3.1 based on observed data. The parameter estimates for citrate synthase obtained from rat kidney, rat liver, and bovine heart are listed in Table 4.2. 

---