HOUSE FLY ADENOSINE TRIPHOSPHATASES AND THEIR INHIBITION BY INSECTICIDAL ORGANOTIN COMPOUNDS.

Abstract

Adenosine triphosphatases (ATPases) in the female house fly, Musca domestica L., have been investigated in relation to their inhibition by organotins and other compounds. The potency of these materials as ATPase inhibitors and house fly toxicants has been compared. The thorax paniculate fraction was used as the ATPase source in most studies. Based on Lineweaver-Burk plots, triethyland triphenyltin and their mono- and disubstituted analogs as well as oligomycin appeared to act as uncompetitive ATPase inhibitors. Competitive inhibition resulted with adenosine diphosphate (ADP) and pyrophosphate. Experiments with organotins, oligomycin, and pyrophosphate as inhibitors and adenosine triphosphate (ATP) and ADP as substrates indicated that two phosphate groups could be removed from ATP by the combined action of ATPase and adenylate kinase. Trisubstituted organotins were the most active tin compounds both as ATPase inhibitors and as toxicants. A good correlation was noted for most trialkyltins between potency for in vitro ATPase inhibition and toxicity to the house fly This correlation was not so clear with trisubstituted organolead and -germanium compounds and was not evident for mono- and disubstituted organotins. Oligomycin, the most potent toxicant by injection, was also the most potent ATPase inhibitor. The insecticidal action of trialkyltins and oligomycin may result from interference with ATPase activity or related processes associated with oxidative phosphorylation.