Mixed activation and mixed inhibition of the oxidoreductase activity of Rhus vernicifera laccase by different Pd2+ ion concentration

Kinetic experiments were performed to study the effects: of Pd2+ ion on the oxidation of 5,6-dibromo-2, 3-dicyanohydroquinone catalyzed by Rhus vernic ifera laccase under condition of pH 3.5 and 30 + 0.1 degrees C. The results showed that the mixed activation could be observed when Pd2+ ion was at lo w concentrations. The competitive and non-competitive activation constants were 9 x 10(-6) and 2 x 10(-6) mol/L, respectively. With the increase of Pd 2+ ion concentration, the activation was gradually converted into mixed inh ibition, and the competitive and non-competitive inhibition constants were 6 x 10(-6) and 32 x 10(-6) mol/L, respectively.