Determining elasticities from multiple measurements of flux rates and metabolite concentrations. Application of the multiple modulation method to a reconstituted pathway.

A recently developed method to determine elasticities by multiple measurements of steady-state flux rates and metabolite concentrations [Giersch, C. (1994) J. Theor. Biol. 169, 89-99] is applied to a reconstituted metabolic pathway. The pathway is the section of glycolysis converting glycerate-3-phosphate to pyruvate. The elasticities of the pathway enzymes are determined from the dependence on effector concentrations of measured steady-state flux rates and steady-state metabolite concentrations. To verify assumptions regarding the dependence of reaction rates on metabolites, flux control coefficients calculated from enzyme elasticities are compared with those estimated by means of the usual enzyme titration. The proposed method is shown to allow experimental determination of enzyme elasticities but requires, like other experiments in metabolic control analysis, a high level of reproducibility and experimental accuracy which may be difficult to attain.