Determining sensitivity of chemical reaction systems by a new function-free method

Chemical reaction pathways are connected in organisms and construct complex networks like metabolic network. One of possible experiments to understand the dynamics of such systems is giving perturbations to reaction rates; to increase/decrease or to knockout enzymes that mediate reactions in the systems. However, it has been considered that the responses of metabolic system in such perturbation experiments are difficult to understand. In this talk, we present a mathematical theory to determine the changes in concentration of chemicals in a reaction system against perturbations to reaction rates from information of network alone. We will show that the responses of chemicals in a system strongly depend on the structure of networks and the positions of perturbed reactions in the network. We derived some general rules showing relations between structure of networks and the response of chemicals. We also show some examples of applications of our theory to some hypothetical or real chemical reaction networks including the metabolic network.