text: In normal usage, the rate-limiting step or rate-determining step is defined as the slowest step of a chemical reaction that determines the speed (rate) at which the overall reaction proceeds. The flux control coefficients do not measure this kind of rate-limitingness. For example, in a linear chain of reactions at steady-state, all steps carry the same flux. That is, there is no slow or fast step with respect to the rate or speed of a reaction. The flux control coefficient, instead, measures how much influence a given step has on the steady-state flux.  A step with a high flux control coefficient means that changing the activity of the step (by changing the expression level of the enzyme) will have a large effect on the steady-state flux through the pathway and vice versa.
  Historically the concept of the rate-limiting steps was also related to the notion of the master step. However, this drew much criticism due to a misunderstanding of the concept of the steady-state.