SEQUENTIAL KINETIC THERMOMETRIC DETERMINATION OF THE ACTIVITY OF PEROXIDASE AND CATALASE USING CATECHOL AS SUBSTRATE AND INHIBITOR FOR THEIR REACTION WITH HYDROGEN-PEROXIDE

A kinetic thermometric method was developed for the determination of p eroxidase by its catalytic effect on the oxidation of catechol by hydr ogen peroxide. The proposed method allows the determination of peroxid ase activity over the range 0.05-0.3 I.U. with an R.S.D. of 2.3%. The method was applied to the determination of peroxidase activity in pres piked matrices of animal origin (rat muscle and liver homogenates). Th e determination of the activity of peroxidase added to rat liver was f ound 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 bou nd to a rat liver matrix, a procedure was developed for the sequential thermometric determination of the activity of both enzymes using cate chol as substrate for peroxidase and inhibitor for catalase.