[Control of the rate of the glucokinase reaction by its elementary stages].
Limitation of an enzymatic reaction by its elemental steps is characterized by so-called control coefficients for (quasi)stationary reaction rate. Established paradigm of "limiting step" cannot describe the control of glucokinase reaction. Flux control is distributed between several elemental steps (ATP binding, ADP release, etc.); this distribution significantly changes when reaction conditions are modified, i.e., changes in glucose or ATP concentrations occur. At about 1 mM ATP and 2-5 mM glucose, impact of ATP binding stage on total flux control is positive and it exceeds 50% if ATP binds after glucose. However, if ATP binds before glucose then control coefficient for ATP binding is negative. At high substrate concentrations, impact of product dissociation on flux control becomes significant. Distribution of control between elemental steps cannot be predicted by changes of Gibbs energy or by the rate constants of elemental steps.
Nartsissov
Ia R
IaR
Kholodenko
B N
BN
D000255:Adenosine Triphosphate / Q000378:metabolism; D005941:Glucokinase / Q000378:metabolism*; D007700:Kinetics; D013816:Thermodynamics
D000255:Adenosine Triphosphate; D005941:Glucokinase