Metabolic control design.

The response of metabolic variables to small parameter changes is quantitatively described by the control coefficients. Their values (the control profile) depend on the rate equations of the enzymes which compose the metabolic system. A procedure, called Metabolic Control Design (MCD), is developed which achieves the "inverse", namely to calculate the kinetic properties of the enzymes which would produce a preconceived control profile when they are embedded in the network. It is shown that the lack of interaction between some variable metabolites and enzymes (i.e. some epsilon-elasticity coefficients are zero), together with the well-known conservation and summation relationships, reduce the number of control coefficients to which arbitrary values can be assigned. A choice of the values of these coefficients constitutes the pre-established control profile. The same procedure can also be used as an in situ method to detect unknown interactions between enzymes and metabolites. Finally, we discuss some implications of the results to the evolution of living organisms.