Evaluation of the interaction of two phenothiazines with 2,2- azinobis (3-ethylbenzthiazoline-6-sulfonate) and potassium iodide in horseradish peroxidase reaction

Abstract

The effect of two phenothiazines: promethazine and chlorpromazine on the initial velocity of horseradish peroxidase (HRP) oxidation of 2,2’-azinobis (3-ethylbenzthiazoline-6-sulfonate) (ABTS) and potassium iodide (KI) was investigated. The phenothiazines enhanced the oxidation of ABTS and KI by HRP. Chlorpromazine (10 μM - 100 μM) produced a proportional increase in the initial velocity of HRP for oxidation of KI and ABTS. Increase in promethazine concentration within the range of 10 μM – 60 μM caused a linear increase in the activity of the enzyme. However, higher concentrations of promethazine (60 μM mM to 100 μM) resulted in a proportionate decrease in HRP activity. Unlike promethazine, chlorpromazine caused a linear increase in oxidation products within a range of 10 μM-100 μM. A comparative study of the phenothiazines showed that chlorpromazine was a better redox mediator of the enzyme than promethazine. Hence, the turnover of the enzymatic products depends on the structure of the phenothiazine.