Nigerian Society for Experimental Biology
Vol. 23, No. 3, 2011, pp. 124-128
Bioline Code: bk11017
Full paper language: English
Document type: Research Article
Document available free of charge
Biokemistri, Vol. 23, No. 3, 2011, pp. 124-128
© Copyright © 2011 Nigerian S°Ciety for Experimental Biology
Suicide inactivation of horseradish peroxidase by excess hydrogen peroxide: The effects of reaction pH, buffer ion concentration, and redox mediation|
Malomo, Sylvia O.; Adeoye, Raphael I.; Babatunde, Lateef; Saheed, Ibraheem A.; Iniaghe, Martin O. & Olorunniji, Femi J.
The inactivation of peroxidases by its oxidant substrate H2O2 limits the usefulness of these versatile enzymes. Here, we investigated the effect of reaction conditions on inactivation of horseradish peroxidase by excess H2O2. Inactivation was more pronounced at pH extremes, indicating that reactions in which the oxidation products induce significant changes in reaction pH could accentuate the loss of peroxidase activity. In reactions carried out in sodium acetate buffer, higher inactivation rates were observed when the buffer ion concentration was increased, an indication that peroxidase might be generating reactive radicals from the buffer molecules. Promethazine exerted a modest protective effect against inactivation; however, higher concentrations of the redox mediator caused a slight increase in inactivation, likely due to the formation of reactive promethazine radicals, which in turn attack the protein via a mechanism different from that caused by excess H2O2. These findings will help in defining the optimal reaction conditions that preserve the activity of the peroxidase molecules.