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 P+ 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 P+ significantly inhibited the triosephosphate production from glucose with an IC SH of about 6.0 W WM. At a similar extension Cu P+ inhibited hexokinase and phosphofructokinase, with an IC SH of 6.2 W WM and 6.4 W WM 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 W WM. 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 P+ equal to the flux IC SH , the response coefficient was 31. The elasticity coefficients for hexokinase and phosphofructokinase at Cu P+ equal to the IC SH were also 31. 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.z 1999 Federation of European Biochemical Societies.

Isozymes of plant hexokinase: Occurrence, properties and functions

“…In animals, HK has been shown to exert a high level of control over glycolytic flux. Thus, values of flux control coefficients between 0.7 and 1 have been measured in mammalian erythrocytes, liver, heart, insulinoma and muscle cells (Rapoport et al, 1974;Torres et al, 1988;Kashiwaya et al, 1994;Wang and Iynedjian, 1997;Puigjaner et al, 1997;Jannaschk et al, 1999). In plants, however, the control coefficient of HK over glycolytic flux has not been assessed.…”

Environmental Degradation at a Public Park in Southern Brazil as Revealed Through a Genotoxicity Test (MN) on Peripheral Blood Cells from Poecilia vivipara (Teleostei)

“…Contrarily, copper concentrations (Tables 2, 3) were higher than the reference values. The impact of copper on the environment, even at low concentrations, is recognized (Jannaschk et al 1999;Chassagnole et al 2003;Carattino et al 2004;Strydom et al 2006). Copper ions are also known to exhibit high affinity with the catalysis of free radicals, with severe consequences in both DNA repair and duplication, thereby inducing genome damage (Hartwig 1995).…”

Inhibition of phosphofructokinases by copper(II)

“…Since there seems to be no consistent correlation between the inhibitory e¡ect of copper-(II) and the molecular mass or structure of the enzymes, the amino acid sequence (and resulting three-dimensional structure of the active site of the enzymes) and therefore the electron donor groups available for reaction with Cu 2 ions are likely responsible for determining some of the sensitivity of the enzymes. Copper(II) has also been shown to coordinate with the phosphate groups of nucleoside triphosphates and to markedly enhance their rate of hydrolysis [16]. This latter e¡ect and the binding of Cu 2 ions to phosphates in general could also contribute to its inhibitory e¡ect, possibly via the phosphoryl donor binding sites of the PFKs [16].…”

“…Copper(II) has also been shown to coordinate with the phosphate groups of nucleoside triphosphates and to markedly enhance their rate of hydrolysis [16]. This latter e¡ect and the binding of Cu 2 ions to phosphates in general could also contribute to its inhibitory e¡ect, possibly via the phosphoryl donor binding sites of the PFKs [16]. …”