Evaluation of an electrochemical method for the analysis of enzymatic inhibition reactions.

An approximate equation for bioelectrocatalitic current was applied to an inhibition reaction analysis of bilirubin oxidase by anion (Cl(-), SCN(-), and F(-)) in order to assess the possibility of the electrochemical method for the analysis of enzymatic inhibition reactions. The approximate equation can be transformed into the Michaelis-Menten form, so that the bioelectrocatalitic current can be analyzed by the usual graphical manner, that is, Lineweaver-Burk, Hanes-Woolf, Dixon and Cornish-Bowden plots, if the rate of inhibition reaction is described as a simple Michaelis-Menten form. From the electrochemical assay, it was found that the inhibitor of Cl(-) and SCN(-) anions exhibit non-competitive inhibition while that of F(-) exhibits competitive inhibition, and their inhibition constants were 220, 45, and 22 mM, respectively. The results were essentially similar to those obtained from the conventional spectrophotometric assay.