Mixed activation and mixed inhibition of the oxidoreductase activity of Rhus vernicifera laccase by different Pd 2+ ion concentration

Kinetic experiments were performed to study the effects of Pd 2+ ion on the oxidation of 5,6‐dibromo‐2, 3‐dicyanohydroquinone catalyzed by Rhus vernicifera laccase under condition of pH 4.5 and 30 ± 0.1°C. The results showed that the mixed activation could be observed when Pd 2 ion was at low concentrations. The competitive and non‐competitive activation constants were 9 × 10 − ‐ 6 and 2 × 10 − ‐ 6 mol/L, respectively. With the increase of Pd 2+ ion concentration, the activation was gradually converted into mixed inhibition, and the competitive and non‐competitive inhibition constants were 6 × 10 − ‐ 6 and 32 × 10 − ‐ 6 mol/L, respectively.