In ‘simple’ metabolic pathways the response to an external signal is readily described in terms of the effect of the signal on its receptor enzyme and the control exerted by that enzyme. We show here that in the response of ‘channelled’ pathways to such a signal, additional terms appear that reflect the direct enzyme-enzyme interactions. They tend to enhance the responsiveness of the pathway. The normalized value of the response is called the signal transduction coefficient. We show that in channelled pathways these coefficients are usually larger than in corresponding non-channelled (simple) pathways.
