INHIBITORY EFFECT OF CADMIUM ACETATE ON SYNAPTOSOMAL ATP-DIPHOSPHOHYDROLASE (EC 3.6.1.5 APYRASE) FROM ADULT-RAT CEREBRAL-CORTEX

ATP diphosphohydrolase (EC 3.6.1.5; apyrase) is an enzyme that can pro mote ATP and ADP hydrolysis to AMP plus inorganic phosphate and depend s on divalent cations such as Ca2+ or Mg2+. In previous papers we desc ribed this enzyme in the synaptosomal fraction from the central and pe ripheral nervous system. The present report examines whether cadmium a cetate could affect the in vitro activity of the enzyme in the synapto somal fraction from the cerebral cortex of adult male Wistar rats. Cad mium (Cd2+), a heavy metal with neurotoxic effects, inhibited the enzy me in a concentration-dependent manner. All concentrations tested (0.0 5-1.0 mM) significantly inhibited the hydrolysis of both substrates (A TP and ADP), with the exception of 0.05 mM on ATP hydrolysis. The kine tic data indicate a noncompetitive inhibition between the cations Cd2 and Ca2+.