Effects of some chlorinated pesticides on porcine pancreatic and Rhizopus delemar lipase activities.

Abstract

The effects of three classes of chlorinated pesticides, chloroethanes (DDT, etc.), cyclodienes (aldrin, etc.), and chlorophenols (PCP, etc.), on the activities of porcine pancreatic and Rhizopus delemar lipases were studied using water-soluble tripropionin as a substrate. The effects were examined by three different procedures : (I) preincubation of lipase with pesticide and initiation of the enzyme reaction by addition of substrate, (II) preincubation of substrate with pesticide and initiation of the enzyme reaction by addition of lipase, (III) addition of pesticide after initiation of the enzyme reaction. With porcine pancreatic lipase, chloroethanes and cyclodienes exhibited significant activation, increasing the Vmax value and decreasing the Km value, when procedure II was employed, but showed non-competitive inhibition when procedure I or III was employed. With Rhizopus delemar lipase, chloroethanes and cyclodienes exhibited significant activation, increasing only the Vmax value in all three procedures. The activation of pancreatic lipase by chloroethanes was only temporary. Chlorophenols competitively inhibited both lipases in all three procedures.