KINETIC MODEL OF PHOSPHOFRUCTOKINASE-1 FROMESCHERICHIA COLI

Abstract

This paper presents a kinetic model of phosphofructokinase-1 from Escherichia coli. A complete catalytic cycle has been reconstructed based on available information on the oligomeric structure of the enzyme and kinetic mechanism of its monomer. Applying the generalization of the Monod–Wyman–Changeux approach proposed by Popova and Sel'kov35–37to the reconstructed catalytic cycle rate equation has been derived. Dependence of the reaction rate on pH , magnesium, and effectors has been taken into account. Kinetic parameters have been estimated via fitting the rate equation against experimentally measured dependencies of initial rate on substrates, products, effectors, and pH available from the literature. The model of phosphofructokinase-1 predicts (1) cooperativity of binding both fructose-6-phosphate and ATPMg2-, (2) significant inhibition of the enzyme resulting from an increase in total concentration of ATP under the condition of fixed concentration of Mg2+ions, and (3) dual effect of ADP consisting of allosteric activation and product inhibition of the enzyme. Moreover, the model developed can be used in the kinetic modeling of biochemical pathways containing phosphofructokinase-1.