Role of phospholipids in the inhibitory action of DDT and permethrin on the nerve ATPase of lobster, Homarus americanus.

Efforts were made to understand the nature of the site of 1,1-bis-(p-chlorophenyl)-2,2,2-trichloroethane (DDT) inhibition of nerve ATPase. THe phospholipid content of nerve preparations from the walking leg of the lobster was reduced by treating them with phospholipase A, or with a chloroform-methanol mixture at -75 degrees. By these treatments the enzymes lost approximately 70 or 95% of their phospholipids and 50-80% of their Na,K- and Ca-ATPase activities. The lost ATPase activities could be partially restored by the addition of phospholipids, either the ones extracted from the lobster nerves or those from commercial sources. ATPase inhibition by DDT and permethrin was found to be highest in preparations where the phospholipids were removed by the above treatments, next highest with the untreated original enzyme, and least with the reconstituted ATPase regardless of the source of phospholipids used for reconstitution. This tendency was more pronounced in the case of Ca-ATPase. The effects of DDT and permethrin on inhibition of reconstituted Ca-ATPase were higher when the insecticide was first added to the protein portion and the enzyme was then reconstituted with the phospholipids, than when the same amount of insecticide was first added to the phospholipids which were then used for reconstitution.