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.
