Sequential kinetic thermometric determination of the activity of peroxidase and catalase using catechol as substrate and inhibitor for their reaction with hydrogen peroxide

Abstract

A kinetic thermometric method was developed for the determination of peroxidase by its catalytic effect on the oxidation of catechol by hydrogen peroxide. The proposed method allows the determination of peroxidase activity over the range 0.05-0.3 I.U. with an R.S.D. 2.3%. The method was applied to the determination of peroxidase activity in prespiked matrices of animal origin (rat muscle and liver homogenates). The determination of the activity of peroxidase added to rat liver was found to be subject to a matrix effect that was corrected for by using an appropriate matrix-to-substrate concentration ratio. As catalase is thermometrically active at the same pH as peroxidase in its reaction with hydrogen peroxide and behaves similarly towards catechol when bound to a rat liver matrix, a procedure was developed for the sequential thermometric determination of the activity of both enzymes using catechol as substrate for peroxidase and inhibitor for catalase.