AN ATTEMPT TO GENERALIZE THE CONTROL COEFFICIENT CONCEPT

First developed in the case of a stationary flux, the notion of control strength inside a metabolic pathway is extended here to the case of a periodic flux. In this case, the control strength is no more defined on the stationary flux, but on other characteristics of the dynamics like the period or the amplitude, depending on the characteristic whose evolution we wished to describe. We simulated a subsystem of the glycolysis where a periodic behaviour exists and calculated the control strength on the period and on the amplitude of the ATP concentration. The results showed the value of the control coefficients were different on both characteristics: some steps exerts more control on the period than on the amplitude and conversely for other steps. Then, in a given step of the metabolic chain, we tried to relate the control coefficient obtained in the stationary flux situation to the one obtained for the flux amplitude in the periodic situation. We did not observe any continuity phenomenon and we explain that it is due to the qualitative properties of the system. Finally, we think the extension of the notion of control strength to periodic or chaotic motion is a good approach to analyze the way a metabolic step influences specific characteristics of the dynamics.