297 - Electrochemical Oxidation of Catechol and p-aminophenol esters in the presence of hydrolases

Abstract

The half-wave d.c. oxidation potentials of the substrates of alkaline phosphatase: dihydrogen o-hydroxyphenyl phosphate (I) and dihydrogen p-aminophenyl phosphate (II) and that of aryl-β-glucosidase: β-D-glucoside p-aminophenol (III) on platinum electrodes are equal to 681, 516 and 696 mV vs. N.H.E. at pH S.o (I,II) and pH 4.7 (III) respectively. On the pyrographite electrode the substrate oxidation proceeds at nearly the same potentials. Cyclic voltammetry indicates that in the course of electrochemical oxidation o-benzoquinone and p-quinoneimine are formed from the substrate (I) and substrates (II,III), respectively. The products of enzymatic reactions: catechol and p-aminophenol are oxidized at the potentials shifted by 225–300 mV towards the cathodic region. The parameters of enzymatic reactions determined voltammetrically are the following: K M(app) = 1.8 x 10 −4 M (I), 1.7 × 10 −4 M (II) and 5.1 × 10 −4 M (III); V max of the substrates (I) and (III) is reduced to 1.6- and 5.3-fold in comparison with dihydrogen p-nitrophenyl phosphate or β-D-glucoside p-nitrophenol. The results obtained demonstrate the methods of conjugation of electrode processes with the reactions catalyzed by hydrolases.