Practical Determination of Control Coefficients in Metabolic Pathways

Abstract

It is obvious, not only for people working in metabolic control, that theory and practice can share common objectives but rarely share common roads, and it is often very difficult to put together in the same road theorists and experimentalists. In our opinion, metabolic control theories have also illustrated the difficulties in putting together these two disciplines: the hard nomenclature given by some control theories that is not easy for “test-tube” workers to follow; and the difficulties in directly measuring fluxes, intermediate concentrations or elasticity coefficients — terms introduced and popularized by metabolic control theory. In a given metabolic pathway, control of flux is exerted by the enzymes of the system. The direct calculation of flux sensitivities ∂lnJ/∂lnE i where J denotes a particular flux and E i the concentration of an enzyme, implies calculation of flux before and after a small addition of enzyme.This is often extremely difficult to achieve. With this regard indirect methods exist by which local properties (elasticity or special elasticity coefficients) are calculated first. Then control coefficients are calculated by using the equations corresponding to the theorems of metabolic control theory.