Abstract:
Peroxidase (EC 1.11.1.7) extracted from Gongronema latifolium was purified, on a two-step purification process of ammonium sulphate precipitation followed by dialysis. The enzyme was purified 6.8 fold with a specific activity of 2.04 when o-dianisidine was used as substrate. When the enzyme was subjected to different concentrations of hydrogen peroxide and o-dianisidine, the peak activity was 17.75µ/ml at 5mM for hydrogen peroxide and for o-dianisidine the peak activity was 2.4µ/ml observed at 0.4mM. The optimum pH and temperature were at pH 7.0 and 30oC respectively. The Km and Vmax for hydrogen peroxide were 1.8mM and 20u/ml and o-dianisidine had Km of 0.12mM and Vmax of 3.3 µ/ml. The inactivation of peroxidase extracted from Gongronema latifolium by hydrogen peroxide was time dependent and it also showed a biphasic inactivation curve with the initial fast phase and a slower second phase. About 20% protection of the enzyme against inactivation was obtained when 1mM ascorbate was incubated in all the concentrations of hydrogen peroxide while o-dianisidine had above 15% in all the concentrations. Spectral studies, indicated the peak at soret band as 381 nm for the native enzyme, and when the enzyme was incubated with hydrogen peroxide, there was a shift in the soret band of the enzyme from 381nm to 389nm. Increases in the concentration of hydrogen peroxide lead to decreases in the absorbance peak at the soret band of the enzyme and also reduction of size of Soret band. There were elevations in the absorbance peak when1mM ascorbate and 0.4mM o-dianisidine were incubated with the enzyme at different concentrations of hydrogen peroxide
