COENZYME CYCLES AND METABOLIC CONTROL ANALYSIS - THE DETERMINATION OFTHE ELASTICITY COEFFICIENTS FROM THE GENERALIZED CONNECTIVITY THEOREM

Metabolic control analysis allows one to express the elasticity coeffi cients (which describe the ''local'' kinetic features of enzymes) in t erms of the control coefficients (quantitative indicators of the ''glo bal'' control properties). However, when coenzymes (or metabolites lin ked by conservation constraints) are present in the pathway this proce dure yields the ''apparent'' values of elasticity coefficients that co rrespond to the kinetic responses of the enzymes to such a simultaneou s change of the coenzyme forms which leaves the total concentration of these forms unchanged (e.g., NAD(+) + NADH in the glycolysis). We sho w that a generalised connectivity theorem (Kholodenko et al, Fur. J. B iochem. (1994) 225, 179-186) makes it possible to express the elastici ty coefficients with respect to every coenzyme form separately. Such e xpressions include (i) the control coefficients and (ii) the responses to changes in the total concentrations of the coenzymes.