Application of metabolic control analysis to the study of toxic effects of copper in muscle glycolysis

Abstract

Experimental and model studies have been performed to characterise the effects of Cu 2+ on the activities of individual glycolytic enzymes and on the flux and internal metabolite concentrations of the upper part of glycolysis in mouse muscle extracts. Cu 2+ significantly inhibited the triosephosphate production from glucose with an IC 50 of about 6.0 μM. At a similar extension Cu 2+ inhibited hexokinase and phosphofructokinase, with an IC 50 of 6.2 μM and 6.4 μM respectively, whereas the effects on the activities of aldolase, phosphoglucose isomerase and the internal metabolite levels were not significant. Flux control coefficients and flux response coefficients were determined in the presence of copper concentrations between 0 and 10 μM. The same values of flux control coefficients for hexokinase and for phosphofructokinase (0.8 and 0.2 respectively) were found in absence and in presence of copper. At Cu 2+ equal to the flux IC 50, the response coefficient was −1. The elasticity coefficients for hexokinase and phosphofructokinase at Cu 2+ equal to the IC 50 were also −1. A mathematical model was used to analyze the effect of copper on glycolysis under different conditions using experimental kinetic parameters and rate equations for enzymatic reactions of the upper part of glycolysis.