Effects of Ethylenediaminetetraacetic Acid and Some Chlorides of Divalent Metals on the Initial Velocity of Crude Peroxidase from Watermelon Rind

Abstract

Aim: This study investigated the effects of ethylenediaminetetraacetic acid (EDTA) and some chlorides of divalent metals on the initial velocity of crude peroxidase from watermelon rind 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 September 2023 to November 2023. Methodology: The kinetics of the oxidation of Guaiacol by the crude peroxidase from the rind of watermelon in the presence of varying concentrations of EDTA and the chloride salts of iron, copper was determined spectrophotometrically by monitoring the oxidation of Guaiacol to produce a brown tetraguaiacol at a wavelength of 470nm.  The various salt concentrations were varied between 0.5 mM and 3 mM.  Each of the reaction mixtures used in the kinetic study comprised; 2.3 mL of 0.6 M sodium acetate buffer (pH 5.4), 0.2 mL of 0.02 mM Guaiacol, 0.1 mL of crude extract, 0.2 mL of varying concentration chloride salt, 0.2 mL of 2 mM of H2O2 added last to start the reaction. The final concentration of H2O2 in the 3 mL assay was 0.13 mM. The total volume of the reaction mixture was 3 mL. The absorbance was read every 2 seconds for one minute after adding hydrogen peroxide using a stop-clock. The control had no metal ion but replaced with distilled water Results: Results showed that EDTA reduced the activity of the enzyme in a concentration dependent manner. CuCl2 and FeCl2 activated the enzyme and FeCl2 being a better activator within the salt concentration range of 0.5 mM to 3 mM. Conclusion: These findings are of great importance to industries in understanding the mechanism of action of peroxidase from the rind of watermelon, especially as the search for cheap and alternative sources of peroxidases continues.