Kinetics of Oxidation of 3-Aminopyridin-2(1H)-ones by Hydrogen Peroxide in the Presence of Horseradish Peroxidase

The aim of the present work was to estimate the kinetic parameters of oxidation of some 3-aminopyridin-2(1H)-ones by hydrogen peroxide catalyzed by horseradish peroxidase and the affinity of horseradish peroxidase towards these compounds. It was shown that the oxidation of 3-aminopyridin-2(1H)-ones follows pseudo-first-order kinetics. It was also found that a hyperbolic decline in the observed rate constant (kobs) occurred with increasing initial concentrations of 3-aminopyridin-2(1H)-ones. The dependence of kobs on enzyme concentration was linear, suggesting competitive inhibition of oxidation by the reaction product. It was found that the increased polarity of the substituent at the 4th position led to the rise in the rate of oxidation of the pyridinones. The Vmax/Km values were also greater for compounds bearing polar substituent at the 4th position. This kinetic parameter (Vmax/Km) reflects the substrate specificity of enzyme. Data obtained help better understand the mechanisms of interactions between horseradish peroxidase and 3-aminopyridin-2(1H)-ones suggesting that 3-aminopyridinones can be used for the development of a rather sensitive method for detection of hydrogen peroxide and modification of ELISA.