Comparison of the influence of Cu, Zn, and Cd on the activity and kineticsof free and immobilized acid phosphatase

The influence of Cu, Zn, and Cd on the activity and kinetics of acid phosph atase immobilized by two soil clays, kaolin or goethite was investigated. T he ability of Cu to inhibit the enzyme activity was higher than that of Zn in all the enzyme complexes examined. The ability of Cd was negligible. The inhibitory effects of Cu and Zn on the two soil clay- and kaolin-enzyme co mplexes were much stronger than those on the goethite-enzyme complex. The V -max and K-m values of the enzyme complexes indicated that both Cu and Zn d ecreased the maximum reaction velocity of the enzymes, but increased the af finity of the enzymes for the substrate. The degree of the decrease and inc rease was higher in the Cu systems than in the Zn systems.