Effects of Chlorides of Lead and Some Transition Metals on the Kinetics of Crude Peroxidase from Watermelon Seeds

Aims: This study investigates the effect of chlorides of lead and some transition metals on the kinetics of crude peroxidase from watermelon seeds

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 the crude enzyme from the seeds of watermelon, 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 except for nickel chloride, chloride salts of Pb2+, Hg2+, and Fe2+ had peroxidase activating effects. Mercury chloride and lead chloride proportionately increased the enzyme activity within a salt concentration range of 1.5 and 3 mM. In comparison, ferric chloride had an optimum concentration of 2.5 mM for peroxidase activation; mercury chloride had the highest peroxidase activation effect compared with chlorides of Pb, Ni, and Fe.

Conclusion: These findings are of great importance to industries in understanding the mechanism of action of peroxidase from the seeds of watermelon, especially as the search for cheap and alternative sources of peroxidases continues.