Evaluation of the Effects of Some Metal Chlorides on the Initial Reaction Rate of Crude Peroxidase from Watermelon Peels

Abstract

Aims: This study evaluates the effect of some chloride on the initial reaction rates of crude peroxidase from watermelon peels. Study Design:  In vitro enzyme assay. Place and Duration of Study: Department of Biochemistry, Faculty of Life Sciences, Ambrose Alli University, Ekpoma, Edo State, Nigeria between April 2021 and June 2021. Methodology: The kinetics of crude peroxidase catalyzed oxidation of 3,5,3′,5′-tetramethylbenzidine (TMB) in the presence of varying concentrations of different chloride salts and hydrogen peroxidase was determined spectrophotometrically at 655nm. The assay mixture contained 2.3 mL of sodium phosphate buffer of pH 7.0, 0.1 mL of a crude enzyme from the watermelon peels, 0.2 mL of varying concentration of the respective chloride salts, 0.2 mL of 0.02 mM TMB, and 0.2 mL of 2 mM hydrogen peroxidase added last to start the reaction. Results: Results showed that chloride salts of Pb2+ Hg2+ Fe2+ and Na+ had peroxidase activating effects at low salt concentration (1 mM). The activating effect increased proportionately up to their respective optimum salt concentration.  Further increment of salt concentration above their respective optimum value lead to a decrease in initial reaction rate of the crude enzyme. Within a chloride concentration range of 0.025 mM to 3 mM, the highest activating effect recorded was in the order Pb2+ > Fe2+ > Na+ > Hg2+.. Results show that Pb2+ had the highest enzyme activating effect at the lowest concentration (0.5 mM) of the salt when compared with other salts within the same concentration range. Conclusion: These findings are of great significance in research to understanding the mechanism of action of peroxidase from the peels of watermelon, especially as the search for cheap and alternative sources of peroxidases continues.