Purification and Studying Some Characters of Laccase Enzyme from Irradiated Pleurotus Ostreatus ATCC 56270

Purification of laccase enzyme by anion exchange chromatography using DEAE sepharose and sephacryl HR are successful in purifying laccase. SDS- PAGE is the determined of laccase molecular weight which is 75 KDa. The optimum ph for activity was 5 and for stability was 6.5-7.5. The optimum temperature for activity was 35 degree C and stability of the enzyme was stable up to 55 degree C, the enzyme retained 100% of its activity after 20 minutes incubation, 85% of its activity after 1h incubation at the same temperature. The activation energy (E_act) of the purified laccase between 20 degree C and 45 degree C at its optimum ph was 16.3 k Jmol^-1. The apparent Km value of the enzyme for ABTS was estimated to be 1.4 m M under standard assay conditions, k_cat value of ABTS was calculated to be 3450 min^-1 and V_max is the maximum initial rate in the Michaelis-Menten equation (1.2 μmol L^-1 min^-1). Microencapsulation of laccase exhibited that free laccase (35 U/ml) has higher activity than encapsulated laccase (24.3 U/ml)