Peroxidase from Eichhornia crassipes leaf was purified 23.58 fold with 18.58% yield by means of (NH 4 ) 2 SO 4 precipitation, ion exchange and Sephadex G-75 gel filtration chromatography. Optimum temperature and substrate-dependent pH optimum for enzyme activity were 40 °C and pH 4.0, 9.0 and 6.0 for 2,2'-azino-bis-(3-ethylbenzthiazolin)-6-sulfonate (ABTS), guaiacol and pyrogallol, respectively. The enzyme had high pH stability and moderate thermal stability at temperatures up to 60 °C; the activation energy of inactivation of the enzyme was ~122.29 kJ mol -1 . Temperature-denaturing and spontaneous recovery were shown to be time-dependent while Ca 2+ -enhanced recovery of the denatured enzyme was in a time-dependent manner. The enzyme showed preferential affinity for ABTS over guaiacol and pyrogallol with K M values of 31.11, 21.91 and 6.45 mM respectively. It was reversibly inhibited by Pb 2+ , Hg 2+ and EDTA while urea only caused loss of ~30.40% activity after 60 min of incubation. E. crassipes leaf peroxidase has potential use for broad range of applications.

Peroxidases are widely distributed in nature and are used in multiple industrial applications. Sources of peroxidases with notable stability are therefore being explored for commercial purposes. Pistia stratiotes leaf peroxidase was purified and characterized. It exhibited maximum activity at pH 6.0 after 10 minutes of incubation, which shifted to pH 6.5 after 60 minutes of incubation. Peroxidase from P. stratiotes leaf showed moderate stability after heating at 50ºC for 60 minutes and at 60ºC for 30 minutes. This enzyme was strongly inhibited by EDTA while urea had only a slight denaturing effect with approximately 65% of the activity retained after 60 minutes exposure. There was reduction in P. stratiotes leaf peroxidase activity in the presence of Pb 2+ (67%), Hg 2+ (70%), Ni 2+ (75%), Cu 2+ (12%), Co 2+ (60%), Ca 2+ (45%) and Mn 2+ (65%) at 6mM concentration. Acetone activated the enzyme in a concentration-dependent manner while the presence of methanol and ethanol in the reaction mixture led to 16% decrease in the activity of the enzyme at 20% concentration. Results obtained from this study revealed that P.stratiotes leaf peroxidase is moderately stable and thus has potential for some industrial applications.