Inhibition of creatine kinase activity and alterations in electrophoretic mobility by palladium ions

The toxicological consequences of increased levels of palladium in the environment have not yet been assessed. In this paper, the effect of palladium ions (Pd) on purified rabbit muscle creatine kinase (CPK-MM) and on human serum CPK-MM was examined. When rabbit muscle CPK-MM was treated with Pd, a concentration-dependent inhibition of enzyme activity with a calculated Ki of 0.16 mumol, associated with a marked increase in a electrophoretic mobility of the enzyme toward the anode, was observed. Pd exerted the same effect of human serum CPK-MM, but to a lesser extent. Analysis of binding of Pd to CPK-MM by a colorimetric competitive-binding technique, using chlorpromazine-chromophore, as well as by a dialyzing technique, indicated that the cation may form an extremely strong complex with essential SH groups of the enzyme.